Crescent Point and Cation could not immediately be reached for comment.
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Teens across the world are calling for cation against climate change
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Teens across the world are calling for cation against climate change.
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Of course, the big question is: will Trump ruin our Trump-cation?
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My peers need to understand that "corona-cation" is no joking matter.
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"Winter Fun-Cation," drop your kids off for some winter break fun. Feb.
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Make sure your bae-cation is one to remember — without the logistical headaches.
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Expedition Unknown is part of the Travel Channel's "Chill-cation" programming event, which airs Dec.
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But it made a cation, ensuring other similar legal fights could be ruled on differently.
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ISS in April recommended that shareholders vote for Cation board candidates Dallas Howe and Herbert Pinder.
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So let us hope that for the next 17 days, we can all have a Trump-cation.
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We are gathered here today to help you upgrade your summer getaway from vacation to Bey-cation.
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Cation was founded by Sandy Edmonstone, a former deputy head of global oil and gas at Macquarie Capital.
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But what about the more unusual forms of body modi cation that involve cutting and shaping the body?
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Following the split, Kruger jetted off to Sri Lanka for a tropical "work-cation" to film a new commercial.
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Cation called for changes in the board last month, citing the share value that was lost in recent years.
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" Cully posted his own photos from the "day-cation," writing: "So thankful for time shared with my family & friends!
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Cation, which owns a 0.3 percent stake in Crescent Point, began its public push for change at the company last month.
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Crescent Point, whose stock has underperformed the broader market in recent years, is under pressure from Cation Capital to change its board.
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But let's pray that for at least a few of those days, we can all get the Trump-cation we have earned.
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Alberta-based Cation, which owns a 0.3 percent stake in Crescent Point, began its public push for change at the company last month.
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The company, whose stock has underperformed the broader market in recent years, in May won a proxy fight with activist investor Cation Capital.
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ISS recommended shareholders to vote for candidates Dallas Howe and Herbert Pinder nominated by Cation, and asked to vote 'withhold' for the rest two nominations.
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Private investment firm Cation Capital said it intends to nominate four candidates to Crescent Point Energy's board next month at the company's annual shareholders meeting.
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Traditional tribal practices such as scari cation and earlobe stretching have become a part of our culture and can occasionally be seen on the streets.
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Calgary, Alberta-based Crescent Point, whose stock has underperformed the broader market in recent years, is under pressure from Cation Capital to change its board.
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So much of politics today is about artifice and obfus cation, and that extends to the standard political memoir, many of which seem artificial to me.
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"Home is my tranquility—my stay-cation—and through my passion for home design and experiences, I want to design a beautiful home space for you."
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" To more deeply explore the topics touched on in "Behind the Racquet," Cation has added Rubin as a co-host on his podcast, "The Coffee Cast.
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I am taking full advantage of my mom-cation and lay in bed and read for a few minutes before turning out the light for an early night.
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I'm excited to meet some new team members, but mostly excited for my mom-cation (even though I know I am going to miss that chicken nugget something awful!).
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And as they have succeeded, these megacomplexes — and other hybrid sports/vacation destinations like them — have become staples of yet another growing youth sports phenomenon: the tourna-cation circuit.
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Moreover, nearly three-quarters of millenials took at least one "micro-cation," with just over a quarter of millenials taking three "micro-cations" in the same year long period.
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The proxy fight, the biggest in the Canadian energy sector in at least about four years, was closely followed by investors and brought to the forefront new activist investor Cation.
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"Couples should keep in mind that a bae-cation is about experiencing a destination together," said Oneika Raymond, 35, a Travel Channel host and author of the blog Oneika the Traveller.
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ISS said Cation, which owns a 0.3 percent stake in Crescent, has made a "reasonably compelling case" for change at the board, including to enhance profitability and to ensure proper alignment of executive compensation.
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CALGARY, May 4 (Reuters) - Shareholders of Crescent Point Energy Corp voted the Canadian energy producer's full slate of directors after a contentious battle with activist investor Cation Capital, Crescent spokeswoman Andrée Morier said on Friday.
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Pau's stay-cation continues, however he is using the whole entire country of Spain for his low-key jaunts instead of a trip to the local museum or sad public pool like the rest of us.
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The battery Dr Bettinger has come up with has a melanin cathode, an anode of sodium titanium phosphate, which is also non-toxic, and an aqueous electrolyte that can be charged with any soluble cation desired.
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"I think a lot of the players have not felt that they've had a voice, or an outlet where they could express these more difficult things," said Mike Cation, who travels as an embedded commentator on the Challenger Tour.
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Cation Capital, a private investment firm led by the former deputy head of global oil and gas at Macquarie Group, last week disclosed its intention to nominate four candidates to Calgary-based Crescent's board at a shareholders meeting next month.
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TORONTO, May 2 (Reuters) - Canadian energy producer Crescent Point Energy Corp is poised to win support for its director nominees based on preliminary counting of votes, shrugging off opposition from activist investor Cation Capital, according to sources familiar with the situation.
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Kimpton Hotel Allegro, in Chicago, is offering "Tax-Cation," which includes accommodations without the city's 17.4 percent accommodation tax (the hotel covers the fee), a $25 daily food and beverage credit and a welcome amenity of prosecco and chocolate gold coins.
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Culpo and McCaffrey have been on fire lately ... they recently had their belated Christmas together and had a lil bae-cation before getting back to L.A. The duo has been together since early 2019 ... and they're off to one helluva start to 2020.
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Or how about the few days I took off from work for a little stay-cation a couple years ago when I played Diablo 3 for roughly 15 hours every day for three and a half days straight, forgetting to eat and completely neglecting everything else in my life?
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Though momentarily stalled, the players took it in stride, with Krueger even hitting the ball in the direction of the noise (which starts at 0:15, in case you're interested in getting to the good parts.) At first, announcer Mike Cation thought that the noises were coming from an "adult film" playing from a phone somewhere in the stands.
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The values for the relative cation reactivities are −0.4 for the malachite green cation, +2.6 for the benzenediazonium cation, and +4.5 for the tropylium cation.
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Cation occlusion is now considered an essential property of all ATP-driven cation pumps and also other coupled cation transport systems (e.g. cation exchangers or co-transport proteins).
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Cation–π interaction between benzene and a sodium cation. Cation–π interaction is a noncovalent molecular interaction between the face of an electron-rich π system (e.g. benzene, ethylene, acetylene) and an adjacent cation (e.g. Li+, Na+).
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For example, methane, CH4, obeys the conditions for the ionic model with carbon as the cation and hydrogen as the anion (or vice versa, since carbon and hydrogen have the same electronegativity). For compounds that contain cation-cation or anion-anion bonds it is usually possible to transform these homoionic bonds into cation-anion bonds either by treating the atoms linked by the homoionic bond as a single complex cation (e.g., Hg22+), or by treating the bonding electrons in the homoionic bond as a pseudo-anion to transform a cation-cation bond into two cation - pseudo-anion bonds, e.g., Hg2+-e2−-Hg2+.
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Adapted from In the solvolysis of spiro-vinyl triflate, the formation of a vinyl cation intermediate through a concerted process drives further rearrangements that involve the formation of a completely different cyclic structure. Ring expansion can also be achieved through the rearrangement of a vinyl cation. 1,2-hydride shift in vinyl cation to form another vinyl cation isomer. Adapted from The second class of rearrangements, the vinyl cation rearranges to form another vinyl cation isomer.
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1,2-hydride shift in vinyl cation. Adapted from Orbital interactions in vinyl cation to allyl cation rearrangement. Adapted from Vinyl cations undergo 1,2-hydride shifts to form an allyl-stabilized cation. 1,2-hydride shifts are fairly common in alkyl cations and is fast in the NMR time scale.
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The reintroduction of the pyrophosphate group to the cation produces GPP isomer, known as linalyl pyrophosphate (LPP). LPP then forms a resonance-stable cation by losing its pyrophosphate group. Cyclization is then completed thanks to this more favorable stereochemistry of the LPP cation, now yielding a terpinyl cation. Finally, a 1,2-hydride shift via a Wagner-Meerwein rearrangement produces the terpinen-4-yl cation.
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The conversion of GPP to alpha-terpinyl cation. The α-terpinyl cation (5) then undergoes a 1,2 hydride shift via a Wagner–Meerwein rearrangement, leading to the formation of the terpinen-4-yl cation (6).
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Humic substances account for 50 – 90% of cation exchange capacity. Similar to clay, char and colloidal humus hold cation nutrients.
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For example, the methanol radical cation fragments into a methenium cation CH3+ and a hydroxyl radical. In naphthalene the unfragmented radical cation is by far the most prominent peak in the mass spectrum. Secondary species are generated from proton gain (M+1) and proton loss (M-1). Some compounds containing the dioxygenyl cation can be prepared in bulk.
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Two types mannose-6-phosphate can recognize phosphorylated saccharide. One is cation- dependent and the other does not require cation to activate.
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0]hexyl cation is analogous to the previously well-studied aromatic cyclopropenyl cation. Like the cyclopropenyl cation, positive charge is delocalized over three equivalent carbons containing two π electrons. This electronic configuration thus satisfies Huckel's rule (requiring 4n+2 π electrons) for aromaticity. Indeed, Winstein noticed that the only fundamental difference between this aromatic propenyl cation and his non-classical hexyl cation was the fact that, in the latter ion, conjugation is interrupted by three -- units.
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The salt is also soluble in benzene. In crystals grown from a benzene solution the solvent co-crystallizes and a cation is completely separated from the anion. In the cation three benzene molecules surround hydronium forming pi-cation interactions with the hydrogen atoms. The closest (non-bonding) approach of the anion at chlorine to the cation at oxygen is 348 pm.
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The most established and well-known homoaromatic species are cationic homoaromatic compounds. As stated earlier, the homotropenylium cation is one of the most studied homoaromatic compounds. Many homoaromatic cationic compounds use as a basis a cyclopropenyl cation, a tropylium cation, or a cyclobutadiene dication as these compounds exhibit strong aromatic character. center In addition to the homotropylium cation, another well established cationic homoaromatic compound is the norbornen-7-yl cation, which has been shown to be strongly homoaromatic, proven both theoretically and experimentally.
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The Cl/H exchange can then be undergone via reaction with K[HB(s-Bu)3] to give the germylene hydride cation in 91% yield. Synthesis of first stable monomeric germanium(II) hydride cation (a germyliumylidene hydride) The germylene hydride cation was also further reacted with the trityl cation, [Ph3C]+[B(C6F5)4]−, as a hydride scavenger, which resulted in the formation of an adduct with the three-coordinate germylene hydride cation acting a donor and a two-coordinate Ge(II) dication as an electron acceptor.
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Trimethylsulfonium (systematically named trimethylsulfanium and trimethylsulfur(1+)) is an organic cation with the chemical formula (CH3)3S+ (also written as ). It is the simplest sulfonium cation.
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Three types of conductivity measurement are usually done: # Specific conductivity, # Cation conductivity and # De-gassed cation conductivity. There is a difference between these three types of measurements. # Specific conductivity gives overall conductivity value of the sample and is the most generic measurement # Cation conductivity is conductivity measurement after the Cation Column. At the Cation Column, the H+ resins replace the positive ions of all dissolved matter in the solution. When this happens, the treatment chemicals, which are desired ones (and are of basic or alkaline in nature) get converted to H2O, i.e. water. (e.g.
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In organic chemistry, the term 2-norbornyl cation (or 2-bicyclo[2.2.1]heptyl cation) describes one of the three carbocations formed from derivatives of norbornane. Though 1-norbornyl and 7-norbornyl cations have been studied, the most extensive studies and vigorous debates have been centered on the exact structure of the 2-norbornyl cation. The 2-norbornyl cation has been formed from a variety of norbornane derivatives and reagents.
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This allows the baccharenyl double bond to attack the secondary positive charge and forms a pentacyclic ring system to yield the tertiary lupanyl cation. A Wagner-Meerwein 1,2-alykl shift will occur to form the hexacyclic ring system and the secondary oleanyl cation. This is followed by a Wagner-Meerwein 1,2-methyl shift to create the tertiary taraxasteryl cation. This cation is the last intermediate in the taraxasterol pathway.
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Triphenylmethyl hexafluorophosphate is an organic salt with the formula or , consisting of the triphenylmethyl cation and the hexafluorophosphate anion] . The cation is also called triphenylcarbenium, trityl cation, or tritylium.U. S. National Institutes of Health (2019) "PubChem ID 2723954 - Triphenylcarbenium hexafluorophosphate". Entry in NCBI's PubChem database, accessed on 2019-07-25.
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In water the H+ "cation" exists as an H13O6+ ion, with a delocalised proton in a central OHO group.Stoyanov et al. Nitrogen forms an N5+ pentazenium cation; bulk quantities of the salt N5+SbF6− can be prepared. Coincidentally, the NH4+ ammonium cation behaves in many respects as an alkali metal anion.
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Structure of , the parent phosphonium cation. The phosphonium (more obscurely: phosphinium) cation describes polyatomic cations with the chemical formula (R = H, alkyl, aryl, halide). They are tetrahedral and generally colorless.
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Chemistry of the Elements (2nd Edn.), Oxford: Butterworth-Heinemann. . Analogous selenates also occur. The possible combinations of univalent cation, trivalent cation, and anion depends on the sizes of the ions. A Tutton salt is a double sulfate of the typical formula , where A is a univalent cation, and B a divalent metal ion.
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The cation rearranges by a 1,2-migration of a cyclopropane C–C bond to the carbocation, forming the bond shown in blue to give a cyclobutyl carbocation. Subsequently, a second 1,2-migration occurs to form another cyclopropylcarbinyl cation, with the cation resting on a tertiary carbon. This resulting carbocation is then ring-opened by a hydride delivered by NADPH, giving squalene, which is then released by SQS into the membrane of the endoplasmic reticulum. 434x434px While cyclopropylcarbinyl-cyclopropylcarbinyl rearrangements can proceed through discrete cyclobutyl cation intermediates, the supposed cyclobutyl cation could not be trapped in model studies.
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The general structure of an iminium cation An iminium cation in organic chemistry is a functional group with the general structure [R1R2C=NR3R4]+. They are common in synthetic chemistry and biology.
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The terms "hydrazinium" and "hydrazine" may also be used for the doubly protonated cation , more properly called hydrazinediium or hydrazinium(2+). This cation has an ethane-like structure. Salts of this cation include hydrazinediium sulfate and hydrazinediium bis(6-carboxypyridazine-3-carboxylate), .W. Starosta and J. Leciejewicz (2008), "Hydrazinediium bis(6-carboxypyridazine-3-carboxylate) dihydrate".
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Linear and bridged structure of vinyl cation . Adapted from Resonance structure of β-silyl substituted vinyl cation that exhibits hyperconjugation. The bond angle from the x-ray structure is also noted. Adapted from The simplest vinyl cation, , which is unsubstituted, can have two possible structures, a classical linear or a non-classical bridged structure.
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"Methylmercury" is a shorthand for the hypothetical "methylmercury cation", sometimes written "methylmercury(1+) cation" or "methylmercury(II) cation". This functional group is composed of a methyl group bonded to a mercury. Its chemical formula is + (sometimes written as MeHg+). Methylmercury exists as a substituent in many complexes of the type [MeHgL]+ (L = Lewis base) and MeHgX (X = anion).
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This analysis suggests that MLC1 may be a cation channel.
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Since several classically "electron rich" heterocycles are poor donors when it comes to cation–π binding, one cannot predict cation–π trends based on heterocycle reactivity trends. Fortunately, the aforementioned subtleties are manifested in the electrostatic potential surfaces of relevant heterocycles. 450px cation–heterocycle interaction is not always a cation–π interaction; in some cases it is more favorable for the ion to be bound directly to a lone pair. For example, this is thought to be the case in pyridine-Na+ complexes.
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1,2-methyl and 1,2-hydride shift in the same vinyl cation. Adapted from 1,2-methyl shift in tert-butyl substituted vinyl cation. Adapted from 1,2-methyl shift in cyclic vinyl cation. Adapted from 1,2 methyl shifts also occurs in vinyl cations, and like 1,2-hydride shifts, it also has a higher activation barrier compared to its alkyl cation equivalent. In the protonation of alkynes, both 1,2-hydride and 1,2-methyl shifts may take place, the preference depends on the alkyl substituent since it will dictate the resulting allyl cation product. For t-butyl substituents, 1,2-methyl shifts are preferred, and for isopropyl substituents, 1,2-hydride shifts occur instead.
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Cation exchange at the surface of a soil particleCation-exchange capacity is defined as the amount of positive charge that can be exchanged per mass of soil, usually measured in cmolc/kg. Some texts use the older, equivalent units me/100g or meq/100g. CEC is measured in moles of electric charge, so a cation-exchange capacity of 10 cmolc/kg could hold 10 cmol of Na+ cations (with 1 unit of charge per cation) per kilogram of soil, but only 5 cmol Ca2+ (2 units of charge per cation). Cation-exchange capacity arises from various negative charges on soil particle surfaces, especially those of clay minerals and soil organic matter.
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Solute carrier family 12 member 9 (SLC12A9), also known as cation-chloride cotransporter 6 (CCC6) or cation-chloride cotransporter-interacting protein 1 (CIP1), is a protein that in humans is encoded by the SLC12A9 gene.
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The sum of the cation and anion transport numbers equals 1.
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Atiprimod is an amphiphilic compound and a cation at neutral pH.
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A phosphazenium cation related to PPN+ is {[(CH3)2N)3P]2N}+.
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It wasn't until fifteen years later that this idea was revisited, with Grob and Cseh detecting vinyl cation formation during solvolysis reactions of alpha-vinyl halides in their seminal work. Indeed, for this contribution, Grob has been called “the father of the vinyl cation”. The 1960s saw a flurry of vinyl cation-related research, with kinetics data driving the argument for the existence of the species. Noyce and coworkers, for example, reported the formation of a vinyl cation in acid- catalyzed hydration of phenylporopiolic acid.
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For comparison, allyl cation has a gas- phase rotation barrier of around 38 kcal/mol, a much greater penalty for loss of conjugation. Comparison of hydride ion affinities of propyl cation and allyl cation, corrected for inductive effects, results in a considerably lower estimate of the resonance energy at 20–22 kcal/mol. Nevertheless, it is clear that conjugation stabilizes allyl cation to a much greater extent than buta-1,3-diene. In contrast to the usually minor effect of neutral conjugation, aromatic stabilization can be considerable.
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There are two types of ion exchange chromatography: Cation-Exchange and Anion- Exchange. In the Cation-Exchange Chromatography the stationary phase has negative charge and the exchangeable ion is a cation, whereas, in the Anion- Exchange Chromatography the stationary phase has positive charge and the exchangeable ion is an anion. Ion exchange chromatography is commonly used to purify proteins using FPLC.
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Adapted from Methyl shifts to the vinyl cation. Adapted from Methyl shifts are observed in the addition of tert-butyl cation to but-2-yne. The pentaallyl cation that is formed could be the result of a single 1,3-methyl shift or two consecutive 1,2-metyl shifts. Rearrangement via the double bond could also change the size of a cyclic system.
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The diameter of the selectivity filter is ideal for the potassium cation, but too big for the smaller sodium cation. Hence the potassium cations are well "solvated" by the protein carbonyl groups, but these same carbonyl groups are too far apart to adequately solvate the sodium cation. Hence, the passage of potassium cations through this selectivity filter is strongly favored over sodium cations.
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A counterion will be more commonly referred to as an anion or a cation, depending on whether it is negatively or positively charged. Thus, the counterion to an anion will be a cation, and vice versa.
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With antimony pentafluoride, SbF5, a fluoride acceptor, the ReF6+ cation is formed.
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UV containing cation in this uranyl triflate compound shows an octahedral geometry.
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The ease of generating cyclic vinyl cations depends on the size of the ring system, with vinyl cations residing on smaller rings being more difficult to produce. This trend is supported by calculations showing that the vinyl cation prefers a linear arrangement. Due to the high degree of strain in 3-membered ring systems, the generation of the smallest cyclic vinyl cation, cycloprop-1-enyl cation, remains elusive. The SN1 solvolysis chemistry used to produce other vinyl cations has not proven facile for the cycloprop-1-enyl cation.
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The oxygen atoms are well situated to coordinate with a cation located at the interior of the ring, whereas the exterior of the ring is hydrophobic. The resulting cations often form salts that are soluble in nonpolar solvents, and for this reason crown ethers are useful in phase transfer catalysis. The denticity of the polyether influences the affinity of the crown ether for various cations. For example, 18-crown-6 has high affinity for potassium cation, 15-crown-5 for sodium cation, and 12-crown-4 for lithium cation.
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Examples of \pi-\pi , CH-\pi , and \pi -cation interactions systems are important building blocks in supramolecular assembly because of their versatile noncovalent interactions with various functional groups. Particularly, \pi - \pi , CH-\pi and \pi -cation interactions are widely used in supramolecular assembly and recognition. \pi-\pi concerns the direct interactions between two -systems; and cation-\pi interaction arises from the electrostatic interaction of a cation with the face of the -system. Unlike these two interactions, the CH-\pi interaction arises mainly from charge transfer between the C–H orbital and the -system.
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It is still prepared according to the original procedure from 1909. The cation in basic iron acetate is isostructural with the cation in basic chromium acetate. Both feature octahedral metal centers conjoined by oxo and acetate bridging ligands.
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Despite the capability of the cation exchange chromatography in purification process, hydrophobic interaction chromatography is also employed, usually at the second step as a polishing step. By using relatively small bead-sized cation resin, the cation exchange chromatography can identify and separate between isoforms by the apparent charges in the condition, but hydrophobic interaction chromatography is capable of identification and separation of the isoforms by their hydrophobicity.
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DMAPP ionizes to its respective allylic cation that undergoes electrophilic addition to the double bond of IPP. Upon loss of a proton, geranyl diphosphate (GPP) is formed. GPP undergoes an elimination reaction to form its corresponding allylic cation. Electrophilic addition of another IPP unit to the GPP cation results in a tertiary carbocation intermediate that forms a fifteen-carbon farnesyl diphosphate (FPP) upon loss of a proton.
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Already studied by Bischoff (1968), magnesium ion is a long known inhibitor of calcite nucleation and crystal growth. The cation is the second-most abundant cation present in seawater after , as is the second anion after . Although closely resembling , the ionic radius of the naked cation is smaller. Some paradoxical consequences arise between its contrasted electrostatic behavior in the mineral solid phase and in aqueous solution.
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Schiff base formation confirms the biosynthesis of the N-methyl-Δ1-pyrrolinium cation.
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Ketoconazole has been found to inhibit the activity of the cation channel TRPM5.
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The vinyl cation has an intense IR peak at 1987 cm−1 for the C=C+ stretching. More importantly, the bond angles between the vinyl cation carbons and the first carbon of the alkyl substituted was measured to be approximately 180o.
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Nickel ions can act as a cation in salts with many acids, including common oxoacids. Salts of the hexaaqua ion (Ni2+) are especially well known. Many double salts containing nickel with another cation are known. There are organic acid salts.
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Clays, zeolites, and other natural material have a high capacity for cation exchange. They do this by creating a net negative charge by substituting lower-valent cations (e.g. Al3+) with a higher-valent cation (e.g. Si4+) within the mineral structure.
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4 (2011): 121–133. 4\. "Con-di-fi-cation: Black Women, Leadership and Political Power", Feminist Africa, March, 2007.[Reprinted as “Con-di-fi-cation: Black Women, Leadership, and Political Power,” in Still Brave: The Evolution of Black Women’s Studies, eds.
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Cation exchange sorbents are derivatized with functional groups that interact and retain positively charged cations, such as bases. Strong cation exchange sorbents contain aliphatic sulfonic acid groups that are always negatively charged in aqueous solution, and weak cation exchange sorbents contain aliphatic carboxylic acids, which are charged when the pH is above about 5. Strong cation exchange sorbents are useful because any strongly basic impurities in the sample will bind to the sorbent and usually will not be eluted with the analyte of interest; to recover a strong base a weak cation exchange cartridge should be used. To elute the analyte from either the strong or weak sorbent, the stationary phase is washed with a solvent that neutralizes ionic interaction between the analyte and the stationary phase.
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Comparing the quadrupole moment of different arenes is a useful qualitative tool to predict trends in cation–π binding, since it roughly correlates with interaction strength. Arenes with larger quadrupole moments are generally better at binding cations. However, a quadrupole-ion model system cannot be used to quantitatively model cation–π interactions. Such models assume point charges, and are therefore not valid given the short cation–π bond distance.
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It is the loss of a hydrogen from this cation that generates α-terpinene.
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Bond lengths deduced from X-ray crystallography are consistent with a cyclohexadienyl cation structure.
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Ball-and-stick model of the tropylium cation The tropylium ion is an aromatic species with the formula . Its name derives from the molecule tropine (itself named for the molecule atropine). Salts of the tropylium cation can be stable, e.g. tropylium tetrafluoroborate.
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Ethylmercury (sometimes ethyl mercury) is a cation composed of an organic CH3CH2\- species (an ethyl group) bound to a mercury(II) centre, making it a type of organometallic cation, and giving it a chemical formula C2H5Hg+. The main source of ethylmercury is thiomersal.
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The diargon cation, has a binding energy of 1.29 eV. The triargon cation is linear, but has one Ar−Ar bond shorter than the other. Bond lengths are 2.47 and 2.73 ångströms. The dissociation energy to Ar and Ar2+ is 0.2 eV.
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Patterns in the age and context of rock art in the Northern Cape. South African Archaeological Bulletin 44, 73-81. Direct cation ratio dating methods applied at Klipfontein,Whitley, D.S. & Annegarn, H.J. 1994. Cation-ratio dating of rock engravings from Klipfontein, Northern Cape.
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Thus, histamine is normally protonated to a singly charged cation. Histamine is a monoamine neurotransmitter.
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Although seldom used, a hydrogen cycle cation softener will reduce the alkalinity associated with hardness.
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Structure of [2.2.2]-cryptand encapsulating a potassium cation (purple) as determined by X-ray crystallography.
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The process is highly dependent on the solvent, nature of the nucleophile, and moieties in the compound. In primary vinyl cations, a 1,2-hydride is unlikely because of the low stability of the primary vinyl cation because of the low electron-donating capability of hydrogen. However, this is still observed in special cases like in 1-methyl-2-phenylvinyl triflate, where the resulting vinyl cation is resonance-stabilized. Halogen shift in vinyl cation.
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Cryptand with a metal cation demonstrating host–guest chemistry. Cryptands are tricyclic compounds that tightly encapsulate the guest cation via electrostatic interactions (ion-dipole interaction). Chemists use the study of intramolecular and intermolecular non- covalent bonding/interactions in molecules to evaluate reactivity. Such interactions include, but are not limited to, hydrogen bonding, electrostatic interactions between charged molecules, dipole-dipole interactions, polar-π and cation-π interactions, π-stacking, donor-acceptor chemistry, and halogen bonding.
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The trifluorooxonium cation is a hypothetical positively charged polyatomic ion with chemical formula . It is structurally equivalent to the hydronium ion where the hydrogen atoms surrounding the central oxygen atom have been replaced by fluorine, and is isoelectronic with nitrogen trifluoride. This cation would be an example of oxygen in the +4 oxidation state. The cation was shown to be vibrationally stable at all levels of theory applied (HF, MP2, CCSD(T)).
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The methylium cation () exists in the gas phase, but is otherwise not encountered. Some compounds are considered to be sources of the cation, and this simplification is used pervasively in organic chemistry. For example, protonation of methanol gives an electrophilic methylating reagent that reacts by the SN2 pathway: :CH3OH + H+ → Similarly, methyl iodide and methyl triflate are viewed as the equivalent of the methyl cation because they readily undergo SN2 reactions by weak nucleophiles.
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An important piece of early evidence in support of the homotropylium cation structure that did not rely on the magnetic properties of the molecule involved the acquisition of its UV spectrum. Winstein et al. determined that the absorption maxima for the homotropylium cation exhibited a considerably shorter wavelength than would be precited for the classical cyclooctatrienyl cation or the bicyclo[5.1.0]octadienyl compound with the fully formed internal cyclopropane bond (and a localized electronic structure).
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The trihydrogen cation' or protonated molecular hydrogen is a cation (positive ion) with formula ', consisting of three hydrogen nuclei (protons) sharing two electrons. The trihydrogen cation is one of the most abundant ions in the universe. It is stable in the interstellar medium (ISM) due to the low temperature and low density of interstellar space. The role that plays in the gas-phase chemistry of the ISM is unparalleled by any other molecular ion.
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Cation–π interactions can tune the pKa of nitrogenous side-chains, increasing the abundance of the protonated form; this has implications for protein structure and function. While less studied in this context, the DNA bases are also able to participate in cation–π interactions.
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The dihydrogen cation' or hydrogen molecular ion is a cation (positive ion) with formula '. It consists of two hydrogen nuclei (protons) sharing a single electron. It is the simplest molecular ion. The ion can be formed from the ionization of a neutral hydrogen molecule .
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Trimethylsilyl trifluoromethanesulfonate is a source of trimethylsilyl cation. Other more potent sources silylium cations are known.
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Typical aminophosphines undergo oxidation to the oxide. Alkylation, e.g. by methyl iodide, gives the phosphonium cation.
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The group thus proposed the name "tris-homocyclopropenyl"—the tris-homo counterpart to the cyclopropenyl cation.
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Because of the binding to positively charged entities, it can be described as a cation hole.
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Although several reports showed that CsPbX3 NCs could be doped with Mn2+, they accomplished this through the addition of the Mn precursor during the synthesis, and not through cation exchange. Cation exchange can be used to partially exchange Pb2+ with Sn2+, Zn2+, or Cd2+ over the course of several hours. In addition to these cations, gold was also shown to be a suitable candidate for cation exchange yielding a mixed-valent, and distorted, perovskite with the composition Cs2Au(I)Au(III)Br6. A-site cation exchange has also been shown to be a viable route for the transformation of CsPbBr3 to MAPbBr3 and from CsPbI3 to FAPbI3.
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The main reason that EDTA is used so extensively in the standardization of metal cation solutions is that the formation constant for most metal cation-EDTA complexes is very high, meaning that the equilibrium for the reaction: :M2+ \+ H4Y → MH2Y + 2H+ lies far to the right. Carrying out the reaction in a basic buffer solution removes H+ as it is formed, which also favors the formation of the EDTA-metal cation complex reaction product. For most purposes it can be considered that the formation of the metal cation-EDTA complex goes to completion, and this is chiefly why EDTA is used in titrations and standardizations of this type.
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Ferrocenium hexafluorophosphate is an organometallic compound with the formula [Fe(C5H5)2]PF6. This salt is composed of the cation [Fe(C5H5)2]+ and the hexafluorophosphate anion (). The related tetrafluoroborate is also a popular reagent with similar properties. The cation is often abbreviated Fc+ or Cp2Fe+.
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Also, when the cation is formed the central carbon is rehybridised from sp3 to sp2 Orbital hybridisation. This causes the atoms to exhibit a trigonal planar arrangement and shortens the covalent bonds around the central carbon in the cation due to the increase in S character.
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Ferrocenium tetrafluoroborate is an organometallic compound with the formula [Fe(C5H5)2]BF4. This salt is composed of the cation [Fe(C5H5)2]+ and the tetrafluoroborate anion (). The related hexafluorophosphate is also a popular reagent with similar properties. The cation is often abbreviated Fc+ or Cp2Fe+.
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The authors note that in the rate limiting step, a large positive charge develops on the benzylic carbon, indicating that the reaction proceeds through a vinyl cation transition state. Hyperconjugation and hydrogen bonding was evoked to explain the accessibility of the vinyl cation described by Noyce.
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General scheme for electrophilic attack on acetylene. Adapted from Acid-catalyzed hydration of alkynes through vinyl cation intermediate. Adapted from A vinyl cation intermediate is possibly formed when electrophilic moieties attack unsaturated carbons. This can be achieved in the reaction of electrophiles with alkynes or allenes.
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Cyclononatetraenyl cation is an 8π system. Its intermediacy is implicated in the solvolysis of 1. The facile solvolysis of 1 suggests that the cation is stabilized. Computation and experimental evidence suggest that C9H9+ is a rare example of a ground state species that exhibits Möbius aromaticity.
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The nature of the solvent also determines the absolute and relative strength of the bonding. Most data on cation–π interaction is acquired in the gas phase, as the attraction is most pronounced in that case. Any intermediating solvent molecule will attenuate the effect, because the energy gained by the cation–π interaction is partially offset by the loss of solvation energy. For a given cation–π adduct, the interaction energy decreases with increasing solvent polarity.
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Probable cation-transporting ATPase 13A3 is an enzyme that in humans is encoded by the ATP13A3 gene.
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The effects of carpaine may be related to its macrocyclic dilactone structure, a possible cation chelating structure.
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It is found primarily in the kidney, where it may mediate the first step in cation reabsorption.
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Cation–π interactions can catalyze chemical reactions by stabilizing buildup of positive charge in transition states. This kind of effect is observed in enzymatic systems. For example, acetylcholine esterase contains important aromatic groups that bind quaternary ammonium in its active site. Polycyclization enzymes also rely on cation–π interactions.
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Thus, certain alkyl-substituted 2-bicyclo[2.2.1]heptyl cations are now known to adopt classical structures. The nature of bonding in the 2-norbornyl cation incorporated many new ideas into the field’s understanding of chemical bonds. Similarities can be seen between this cation and others, such as boranes.
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Attachment of a cation to causes the complex to cross the bilipidic layer undergoing a flip- flop. The headgroup aligns itself with the phospholipids of the inner sheet and the fatty acid chain interacts with the phospholipids acyl chains. The cation is then delivered into the intracellular medium.
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Argonium (also called the argon hydride cation, the hydridoargon(1+) ion, or protonated argon; chemical formula ArH+) is a cation combining a proton and an argon atom. It can be made in an electric discharge, and was the first noble gas molecular ion to be found in interstellar space.
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The electronic trends in cation–π binding energy are not quite analogous to trends in aryl reactivity. Indeed, the effect of resonance participation by a substituent does not contribute substantively to cation–π binding, despite being very important in many chemical reactions with arenes. This was shown by the observation that cation–π interaction strength for a variety of substituted arenes correlates with the σmeta Hammett parameter. This parameter is meant to illustrate the inductive effects of functional groups on an aryl ring.
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Examples are excited electronic states of NH3+ and the benzene radical cation. Here, crossings between the E and A state APESs amount to triple intersections, which are associated with very complex spectral features (dense line structures and diffuse spectral envelopes under low resolution). The population transfer between the states is also ultrafast, so fast that fluorescence (proceeding on a nanosecond time scale) cannot compete. This helps to understand why the benzene cation, like many other organic radical cation, does not fluoresce.
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UV 193-nm photoionization effectively removes a π-electron from the twofold degenerate E1-HOMO located in the aromatic network of electrons yielding a corannulene radical cation. Owing to the degeneracy in the HOMO orbital, the corannulene radical cation is unstable in its original C5v molecular arrangement, and therefore, subject to Jahn-Teller (JT) vibronic distortion. Using electrospray ionization, a protonated corannulene cation has been produced in which the protonation site was observed to be on a peripheral sp2-carbon atom.
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However, the 2-norbornyl cation can be formed from derivatives of β-(Δ-cyclopentenyl)-ethane, indicating that the pi-bonded resonance structure is significant. The 2-norbornyl cation was one of the first examples of a non-classical ion. Non-classical ions can be defined as organic cations in which electron density of a filled bonding orbital is shared over three or more centers and contains some sigma-bond character. The 2-norbornyl cation is seen as the prototype for non-classical ions.
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The electrostatic flux that links the cation core to its bonding electrons now links the cation core to the anion. In this picture, a cation and anion are bonded to each other if they are linked by electrostatic flux, with the flux being equal to the valence of the bond. In a representative set of compounds Preiser et al. have confirmed that the electrostatic flux is the same as the bond valence determined from the bond lengths using Eq. 2.
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Further, several disparate features of these simulations agree with their experimental counterparts suggesting an alternative interpretation of the experimental results. Zundel cation Two other well-known structures are the Zundel cation and the Eigen cation. The Eigen solvation structure has the hydronium ion at the center of an complex in which the hydronium is strongly hydrogen-bonded to three neighbouring water molecules. In the Zundel complex the proton is shared equally by two water molecules in a symmetric hydrogen bond.
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Hydrogen halides such as hydrogen chloride (HCl) adds to alkenes to give alkyl halides in hydrohalogenation. For example, the reaction of HCl with ethylene furnishes chloroethane. The reaction proceeds with a cation intermediate, being different from the above halogen addition. An example is shown below: :390px #Proton (H+) adds (by working as an electrophile) to one of the carbon atoms on the alkene to form cation 1. #Chloride ion (Cl−) combines with the cation 1 to form the adducts 2 and 3.
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Figure 4 Cation–pi interactions involve the positive charge of a cation interacting with the electrons in a π-system of a molecule. This interaction is surprisingly strong (as strong or stronger than H-bonding in some contexts), and has many potential applications in chemical sensors. For example, the sodium ion can easily sit atop the π cloud of a benzene molecule, with C6 symmetry (See figure 4). Anion–π interactions are very similar to cation–π interactions, but reversed.
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The above are examples of the buffering of soil pH. The general principal is that an increase in a particular cation in the soil water solution will cause that cation to be fixed to colloids (buffered) and a decrease in solution of that cation will cause it to be withdrawn from the colloid and moved into solution (buffered). The degree of buffering is often related to the CEC of the soil; the greater the CEC, the greater the buffering capacity of the soil.
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It employs one cofactor, divalent cation. At least one compound, Chelating agent is known to inhibit this enzyme.
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Zinc transporter ZIP8 is a cation/bicarbonate symporter protein which in humans is encoded by the SLC39A8 gene.
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Some studies have used interesting comparisons in order to probe the energetic stability of the 2-norbornyl cation provided by its delocalized nature. Comparing the rearrangement between the 3-methyl-2-norbornyl cation and the 2-methyl-2-norbornyl cation to that between the tertiary and secondary isopentane carbocations, one finds that the change in enthalpy is about 6 kcal/mol less for the norbornyl system. Since the major difference between these two reversible rearrangements is the amount of delocalization possible in the electronic ground state, one can attribute the stabilization of the 3-methyl-2-norbornyl cation to its non-classical nature. However, some experimental studies failed to observe this stabilization in solvolysis reactions.
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The cation–π interaction is noncovalent and is therefore fundamentally different than bonding between transition metals and π systems. Transition metals have the ability to share electron density with π-systems through d-orbitals, creating bonds that are highly covalent in character and cannot be modeled as a cation–π interaction.
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Heterocycles are often activated towards cation–π binding when the lone pair on the heteroatom is in incorporated into the aromatic system (e.g. indole, pyrrole). Conversely, when the lone pair does not contribute to aromaticity (e.g. pyridine), the electronegativity of the heteroatom wins out and weakens the cation–π binding ability.
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231x231px CW occurs after the polymer chain has grown somewhat on the metal catalyst. The precursor is a 16 e− complex with the general formula [ML2(C2H4)(chain)]+. The ethylene ligand (the monomer) dissociates to produce a highly unsaturated 14 e− cation. This cation is stabilized by an agostic interaction.
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TrpC4 is a member of the transient receptor potential cation channels. This protein forms a non-selective calcium-permeable cation channel that is activated by Gαi-coupled receptors, Gαq-coupled receptors and tyrosine kinases, and plays a role in multiple processes including endothelial permeability, vasodilation, neurotransmitter release and cell proliferation.
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However, a carbon doubly bonded with the ionized carbon can stabilize the ion by resonance. Such cations as the allyl cation, , and the benzyl cation, , are more stable than most other carbocations. Molecules which can form allyl or benzyl carbeniums are especially reactive. Carbenium ions can also be stabilized by heteroatoms.
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These include methenium or methyl cation , methane cation , and methanium or protonated methane . Some of these have been detected in outer space. Methanium can also be produced as diluted solutions from methane with superacids. Cations with higher charge, such as and , have been studied theoretically and conjectured to be stable.
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The force constant of the ArH bond in this is 1.895 mdyne/Å2 (). The argon trihydrogen cation has been observed in the laboratory. ArH2D+, and have also been observed. The argon trihydrogen cation is planar in shape, with an argon atom off the vertex of a triangle of hydrogen atoms.
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Cyclic nucleotide-gated cation channel alpha-3 is a protein that in humans is encoded by the CNGA3 gene.
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The salt consists of a protonated tryptammonium cation and a 3-carboxyacrylate (hydrogen fumarate) anion in the asymmetric unit.
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The most studied cation–π interactions involve binding between an aromatic π system and an alkali metal or nitrogenous cation. The optimal interaction geometry places the cation in van der Waals contact with the aromatic ring, centered on top of the π face along the 6-fold axis. Studies have shown that electrostatics dominate interactions in simple systems, and relative binding energies correlate well with electrostatic potential energy. The Electrostatic Model developed by Dougherty and coworkers describes trends in binding energy based on differences in electrostatic attraction.
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Studies by Dougherty and coworkers confirmed that cation–π interactions are important for binding and activating nAChR by making specific structural variations to a key tryptophan residue and correlating activity results with cation–π binding ability. The nAChR is especially important in binding nicotine in the brain, and plays a key role in nicotine addiction. Nicotine has a similar pharmacophore to acetylcholine, especially when protonated. Strong evidence supports cation–π interactions being central to the ability of nicotine to selectively activate brain receptors without affecting muscle activity.
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One probe for testing whether or not the 2-norbornyl cation is non-classical is investigating the inherent symmetry of the cation. Many spectroscopic tools, such as nuclear magnetic resonance spectroscopy (NMR spectroscopy) and Raman spectroscopy, give hints about the reflectional and rotational symmetry present in a molecule or ion. Each of the three proposed structures of the 2-norbornyl cation illustrates a different molecular symmetry. The non-classical form contains a reflection plane through carbons 4, 5, 6, and the midpoint of carbons 1 and 2.
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Many calculational studies have been used to compare the feasibility of different proposed geometries. Using the quantum semi-empirical method of MINDO/3, researchers were not able to conclude which geometry of the 2-norbornyl cation was most energetically favorable. However, the classical structure was found to be the only potential minimum for the alkyl-substituted 2-methyl-2-norbornyl cation. Additional calculations using Extended Hückel Theory for Molecular Orbitals were found to favor the non-classical geometry of the cation with reflectional symmetry.
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Generation of a vinyl cation reactive intermediate. Adapted from Vinyl cations have been observed as reactive intermediates during solvolysis reactions. Consistent with SN1 chemistry, these reactions follow first order kinetics. Generally, vinylic halides are unreactive in solution: silver nitrate does not precipitate silver halides in the presence of vinyl halides, and this fact was historically used to dispute the existence of the vinyl cation species. The introduction of “super” Leaving group in the 1970s first allowed for the generation of vinyl cation reactive intermediates with appreciable lifetimes.
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ChemFETs can be utilized in either liquid or gas phase to detect target analyte, requiring reversible binding of analyte with a receptor located in the gate electrode membrane. There is a wide range of applications of ChemFETs, including most notably anion or cation selective sensing. More work has been done with cation-sensing ChemFETs than anion- sensing ChemFETs. Anion-sensing is more complicated than cation-sensing in ChemFETs due to many factors, including the size, shape, geometry, polarity, and pH of the species of interest.
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In allyl lithium compounds, the lithium cation coordinates to the face of the carbon π bond in an η3 fashion instead of a localized, carbanionic center, thus, allyllithiums are often less aggregated than alkyllithiums. In aryllithium complexes, the lithium cation coordinates to a single carbanion center through a Li-C σ type bond.
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Divalent cations may also substitute for the monovalent cation K+ in the A site.American Mineralogist (1987) 72:178-187 Charge balance may be achieved in three ways. :Firstly by replacing two monovalent cations by one divalent cation, and leaving an A site vacancy, as in plumbogummite, Pb2+Al3(PO4)2(OH)5.
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Effect of soil pH on cation-exchange capacity The amount of negative charge from deprotonation of clay hydroxy groups or organic matter depends on the pH of the surrounding solution. Increasing the pH (i.e. decreasing the concentration of H+ cations) increases this variable charge, and therefore also increases the cation- exchange capacity.
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Thus, tosylation followed by reduction allows for the deoxygenation of alcohols. In a famous and illustrative use of tosylate, 2-norbornyl cation was displaced from the 7-norbornenyl tosylate. The elimination occurs 1011 faster than the solvolysis of anti-7-norbornyl p-toluenesulfonate. Structures of the 7-norbornenyl cation with p-orbital stabilization.
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An example of a 3c–2e bond is the trihydrogen cation . This type of bond is also called banana bond.
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One cation replaces another. A cation is a positively charged ion or a metal. When it is written in generic symbols, it is written out like this: :X + YZ → XZ + Y Element X has replaced Y in compound YZ to become a new compound XZ and the free element Y. This is an oxidation–reduction reaction wherein element Y is reduced from a cation into the elemental form and element X is oxidized from the elemental form into a cation. Some examples are: # Cu + 2AgNO3 -> 2Ag(v) + Cu(NO3)2 # Fe + Cu(NO3)2 -> Fe(NO3)2 + Cu(v) # Ca + 2H2O -> Ca(OH)2 + H2 (^) # Zn + 2HCl -> ZnCl2 + H2 (^) If the reactant in elemental form is not the more reactive metal, then no reaction will occur.
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It is soft and the density is 2.93±0.01. The unit cell has dimensions :a = 526 pm :b = 909 pm :c = 1025 pm, with an angle between axes of β=101.0°. The tetrahedral cation-oxygen atom distance is 164.1 pm, The distance from the cation to the oxygen in the octahedral plan is 202 pm.
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The allyl cation has two contributing structures with a positive charge on the terminal carbon atoms. In the hybrid structure their charge is +. The full positive charge can also be depicted as delocalized among three carbon atoms. :Delocalization allyl cation The diborane molecule is described by contributing structures, each with electron-deficiency on different atoms.
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The tropylium ion is frequently encountered in mass spectrometry in the form of a signal at m/z = 91 and is used in mass spectrum analysis. This fragment is often found for aromatic compounds containing a benzyl unit. Upon ionization, the benzyl fragment forms a cation (), which rearranges to the highly stable tropylium cation ().
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Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [(C6H5)3P)2N]Cl, often written [(Ph3P)2N]Cl and abbreviated [PPN]Cl or [PNP]Cl. This colorless salt is a source of the PPN+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. PPN+ is a phosphazene.
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Photoproducts from vinyl iodonium salt. Note: products from possible vinyl cation rearrangement not pictured here. Adapted from Recently, vinyl cation reactive intermediates have been generated in photochemical solvolysis reactions. The figure to the right depicts photochemical solvolysis of vinyl iodonium salt, through heterolytic carbon-iodine bond cleavage, to generate a vinyl carbocation and iodobenzene.
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Paraquat is an oxidant that interferes with electron transfer, a process that is common to all life. Addition of one electron gives the radical cation: : [paraquat]2+ \+ e− [paraquat]+. The radical cation is also susceptible to further reduction to the neutral [paraquat]0: : [paraquat]+. \+ e− [paraquat]0 As an herbicide, paraquat acts by inhibiting photosynthesis.
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Very high concentration of bivalent and monovalant cation increase the efficiency of the cleavage reaction. These cations facilitate the base pairing of the ribozyme with the substrate. VS cleavage rate can be accelerated by high cation concentration as well as by increasing RNA concentration. Therefore, a low concentration of any of these is rate-limilting.
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N-Nitrosamides can be prepared starting from N-monosubstituted carboxamides and the nitrosyl cation (which results from the nitrous cation in the presence of strong acids from the nitrous acid), here exemplified for N-methylacetamide (1).Adalbert Wollrab: Organische Chemie. Eine Einführung für Lehramts- und Nebenfachstudenten. 4. Auflage, Springer-Verlag Berlin Heidelberg 2014, , S. 898.
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Structure of quaternary arsonium compound arsenobetaine. The arsonium cation is a positively charged polyatomic ion with the chemical formula . An arsonium salt is a salt containing either the arsonium () cation, such as arsonium bromide () and arsonium iodide (), which can be synthesized by reacting arsine with hydrogen bromide or hydrogen iodide.Muñoz‐Hernández, M. Á. (2006).
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2]nonatrienyl cation was predicted to be destabilised and the corresponding anion predicted to be stabilised by bicycloaromaticity. Bicycloaromaticity has been studied by others in relation to the bicyclo[3.2.2]nonatrienyl cation and in relation to specific carbanions. In 2017 experimental evidence was reported for bicycloaromaticity (dual aromaticity) to exist in a bicyclic porphyrinoid.
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The compound is encountered in nature in the form of complexes where the two inner hydrogen atoms are replaced by a divalent metal cation. When complexed with an iron(II) (ferrous) cation , the molecule is called heme. Hemes are prosthetic groups in some important proteins. These heme- containing proteins include hemoglobin, myoglobin, and cytochrome c.
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Barbarella et al. studied the oligomerization of 3-(alkylsulfanyl)thiophenes, and concluded from their quantum mechanical calculations, and considerations of the enhanced stability of the radical cation when delocalized over a planar conjugated oligomer, that a radical cation mechanism analogous to that generally accepted for electrochemical polymerization was more likely. Given the difficulties of studying a system with a heterogeneous, strongly oxidizing catalyst that produces difficult to characterize rigid-rod polymers, the mechanism of oxidative polymerization is by no means decided. The radical cation mechanism is generally accepted.
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Cationic Acetylcholine binding to a tryptophan residue of the nicotinamide acetylcholine receptor via a cation–π effect. An example of cation–π interactions in molecular recognition is seen in the nicotinic acetylcholine receptor (nAChR) which binds its endogenous ligand, acetylcholine (a positively charged molecule), via a cation–π interaction to the quaternary ammonium. The nAChR neuroreceptor is a well-studied ligand- gated ion channel that opens upon acetylcholine binding. Acetylcholine receptors are therapeutic targets for a large host of neurological disorders, including Parkinson's disease, Alzheimer's disease, schizophrenia, depression and autism.
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In lone- pair-active multiferroics, the ferroelectric displacement is driven by the A-site cation, and the magnetism arises from a partially filled d shell on the B site. Examples include bismuth ferrite, BiFeO3, BiMnO3 (although this is believed to be anti-polar), and PbVO3. In these materials, the A-site cation (Bi3+, Pb2+) has a so-called stereochemically active 6s2 lone-pair of electrons, and off-centering of the A-site cation is favoured by an energy- lowering electron sharing between the formally empty A-site 6p orbitals and the filled O 2p orbitals.
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To back up their suggestion of the non-classical nature of the 2-norbornyl cation, Winstein and Trifan first used kinetic evidence of the increased reaction rate for formation of the 2-exo-norbornyl cation over the 2-endo-norbornyl cation. Other researchers investigated the reaction rate of compounds that could feature anchimeric assistance but could not undergo rearrangements as the norbornyl system could show similar trends in rate enhancement. This has been claimed by some to be definitive evidence for the non-classical picture. But not all agree.
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The vinyl cation is one of the main types of reactive intermediates involving a non-tetrahedrally coordinated carbon atom, and is necessary to explain a wide variety of observed reactivity trends. Vinyl cations are observed as reactive intermediates in solvolysis reactions, as well during electrophilic addition to alkynes, for example, through protonation of an alkyne by a strong acid. As expected from its sp hybridization, the vinyl cation prefers a linear geometry. Compounds related to the vinyl cation include allylic carbocations and benzylic carbocations, as well as aryl carbocations.
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The precursor for the biosynthesis of taraxasterol is squalene. In the first step of this formation squalene is cyclized with molecular oxygen, FAD, and NADPH via the enzyme squalene epoxidase a flavoprotein to yield (2S)-2,3-oxidosqualene. In the second step if the oxidosqualene is folded in the chair conformation in the enzyme a cascade of cyclizations will occur that results in the formation of the dammarenyl cation. The dammarenyl cation is then subjected to an alkyl shift to create a six-membered ring and relieving ring strain to form the baccharenyl cation.
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The first is basicity, which can be created by doing an alkali metal cation exchange. The second is the Si/Al ratio which impacts the cation exchange capacity. To get a higher adsorption capacity, there must be a lower Si/Al ratio in order to increase the cation exchange capacity. ZIFs 68, 69, 70, 78, 81, 82, 95, and 100 have been found to have very high uptake capacity, meaning that they can store a lot of carbon dioxide, though their affinity to it is not always strong.
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The coordination chemistry of neptunium(V) has been extensively researched due to the presence of cation–cation interactions in the solid state, which had been already known for actinyl ions. Some known such compounds include the neptunyl dimer ·8H2O and neptunium glycolate, both of which form green crystals. Neptunium(VI) compounds range from the simple oxalate (which is unstable, usually becoming Np(IV)) to such complicated compounds as the green . Extensive study has been performed on compounds of the form , where M represents a monovalent cation and An is either uranium, neptunium, or plutonium.
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Solute carrier family 22 member 2 (also termed OCT2 or organic cation transporter-2) is a protein that in humans is encoded by the SLC22A2 gene. Polyspecific organic cation transporters in the liver, kidney, intestine, and other organs are critical for elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. This gene is one of three similar cation transporter genes located in a cluster on chromosome 6. The encoded protein contains twelve putative transmembrane domains and is a plasma integral membrane protein.
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Transient receptor potential cation channel subfamily M member 3 is a protein that in humans is encoded by the TRPM3 gene.
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Transient receptor potential cation channel subfamily M member 1 is a protein that in humans is encoded by the TRPM1 gene.
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In chemistry, an oxonium ion is any oxygen cation with three bonds. The simplest oxonium ion is the hydronium ion H3O+.
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Structure of the cation in the salt [Me2N=C(H)tolyl]+OTf− illustrating the near planarity of the iminium functional group..
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Another quaternary ammonium cation used in some formulations is alkyldimethylbenzylammonium (ADBA). The formula is , where n varies between 8 and 18.
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Tiemonium iodide is an antimuscarinic. It is poorly absorbed from the gut. The active moiety is tiemonium, a quaternary ammonium cation.
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In tsumebite copper ions occupy the B sites, and phosphorus and sulfur occupy the T sites. Lead is the large cation.
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In the process of cation attachment, cations (typically H+ or Na+) attach themselves to analyte molecules; the desorption of the cation attachment (e.g., MNa+) can then be realized through the emitter heating and high field. The ionization of more polar organic molecules (e.g., ones with aliphatic hydroxyl or amino groups) in FD-MS typically go through this mechanism.
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The oxidation state +1 can be produced by dissolving cadmium in a mixture of cadmium chloride and aluminium chloride, forming the Cd22+ cation, which is similar to the Hg22+ cation in mercury(I) chloride. :Cd + CdCl2 \+ 2 AlCl3 → Cd2(AlCl4)2 The structures of many cadmium complexes with nucleobases, amino acids, and vitamins have been determined.
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In 1951, it was first suggested that the 2-norbornyl cation could actually be better described when viewed as a nortricyclonium ion. It has been shown that the major product formed from an elimination reaction of the 2-norbornyl cation is nortricyclene (not norbornene), but this has been claimed to support both non-classical ion postulates.
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Ion-attachment mass spectrometry (IAMS) is a form of mass spectrometry that uses a "soft" form of ionization similar to chemical ionization in which a cation is attached to the analyte molecule in a reactive collision: :{M} + {X+} + A -> {MX+} + A Where M is the analyte molecule, X+ is the cation and A is a non-reacting collision partner.
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Organomercury compounds contain at least one carbon bonded to a mercury atom, shown here.Organomercury refers to the group of organometallic compounds that contain mercury. Typically the Hg–C bond is stable toward air and moisture but sensitive to light. Important organomercury compounds are the methylmercury(II) cation, CH3Hg+; ethylmercury(II) cation, C2H5Hg+; dimethylmercury, (CH3)2Hg, diethylmercury, and merbromin ("Mercurochrome").
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Positive charges of soil minerals can retain anions by the same principle as cation exchange. The surfaces of kaolinite, allophane and iron and aluminium oxides often carry positive charges. In most soils the cation-exchange capacity is much greater than the anion-exchange capacity, but the opposite can occur in highly weathered soils, such as ferralsols (oxisols).
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Structure of vanadyl acetylacetonate. Cavansite, a mineral containing the vanadyl cation that illustrates its characteristic color The vanadyl or oxovanadium(IV) cation, VO2+, is a functional group that is common in the coordination chemistry of vanadium. Complexes containing this functional group are characteristically blue and paramagnetic. A triple bond is proposed to exist between the V4+ and O2- centers.
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In organic chemistry, methenium (also called methylium, carbenium, methyl cation, or protonated methylene) is a cation with the formula . It can be viewed as a methylene radical (:) with an added proton (), or as a methyl radical (•) with one electron removed. It is a carbocation and an enium ion, making it the simplest of the carbenium ions.
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The potential energy diagram of this model is characterized by a single energy minimum, where the structure of the cation corresponds to the transition state between the two conformers of the classical view. Classical and Non-classical Potential Energy Surface Figure 1 - Potential Energy Surface (PES) of (a) classical and (b) non-classical view of a hydrogen-bridged cation.
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Development of this technology began in the 1970s. The electrolysis cell is divided into two "sections" by a cation permeable membrane acting as a cation exchanger. Saturated sodium (or potassium) chloride solution is passed through the anode compartment, leaving at a lower concentration. Sodium (or potassium) hydroxide solution is circulated through the cathode compartment, exiting at a higher concentration.
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Removal of a hydride ion from the methylene bridge gives the planar and aromatic cycloheptatriene cation, also called the tropylium ion. A practical route to this cation employs PCl5 as the oxidant. CHT behaves as a diene in Diels–Alder reactions. Many metal complexes of cycloheptatriene are known, including Cr(CO)3(C7H8) and cycloheptatrienemolybdenum tricarbonyl.
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It is isometric,Bonazzi, P., Chelazzi, L., and Bindi, L., 2013. Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral. American Mineralogist 98, 361-366 although it was previously though to be orthorhombic. When compared to a typical spinel, both the octahedral and tetrahedral sites are split due to cation ordering.
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The exact biosynthesis of β-araneosene is not known, however like other diterpenes, it is assumed to originate with geranylgeranyl pyrophosphate. The pyrophosphate dissociates to generate an allylic cation at the tail of the molecule. Next a cascade of cyclizations yields the stable β-araneosene-15-yl cation. Finally, elimination of the adjacent proton yields β–araneosene.
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Hyperpolarization-activated cation channels of the HCN gene family, such as HCN1, contribute to spontaneous rhythmic activity in both heart and brain.
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Ammonium thiocyanate is an inorganic compound with the formula NH4SCN. It is the salt of the ammonium cation and the thiocyanate anion.
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In chemistry, pentadienyl refers to the organic radical, anion, or cation with the formula [CH2CHCHCHCH2]z, where z = 0, −1, +1, respectively.
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The anion has eight valence electrons, the radical seven and the cation six. All three forms are highly reactive and rarely observed.
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The generation of diphosphorus from a diphosphorus bisanthracene adduct has been reported. The synthesis of a stabilized HP2+ cation has been reported.
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Within an ionic crystal, there will usually be some point defects, but to maintain electroneutrality, these defects come in pairs. Frenkel defects consist of a cation vacancy paired with a cation interstitial and can be generated anywhere in the bulk of the crystal, occurring most commonly in compounds with a low coordination number and cations that are much smaller than the anions. Schottky defects consist of one vacancy of each type, and are generated at the surfaces of a crystal, occurring most commonly in compounds with a high coordination number and when the anions and cations are of similar size. If the cations have multiple possible oxidation states, then it is possible for cation vacancies to compensate for electron deficiencies on cation sites with higher oxidation numbers, resulting in a non-stoichiometric compound.
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Transient receptor potential cation channel subfamily V member 5 is a calcium channel protein that in humans is encoded by the TRPV5 gene.
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Cyclic alkenes also exhibit 1,2-methyl shifts upon solvolysis as well. Alkyl shifts in vinyl cation that leads to changes in cyclic system.
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Therefore, it has been used to form single crystals of large cation complexes in high oxidation states without reduction of the metallic complex.
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Hydrogen atom (center) contains a single proton and a single electron. Removal of the electron gives a cation (left), whereas addition of an electron gives an anion (right). The hydrogen anion, with its loosely held two-electron cloud, has a larger radius than the neutral atom, which in turn is much larger than the bare proton of the cation. Hydrogen forms the only charge-+1 cation that has no electrons, but even cations that (unlike hydrogen) still retain one or more electrons are still smaller than the neutral atoms or molecules from which they are derived.
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Figure 2: (a) Explicit resonance structures for the non-classical 2-norbornyl cation. (b) Common depiction of the 2-norbornyl cation, using dashed lines for partial bonds. Advocates of the non-classical nature of the stable 2-norbornyl cation typically depict the species using either resonance structures or a single structure with partial bonds (see Figure 2). This hypovalent interaction can be imagined as the net effect of i) a partial sigma bond between carbons 1 and 6, ii) a partial sigma bond between carbons 2 and 6, and iii) a partial pi bond between carbons 1 and 2.
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TEMPO-unit and the negative terminal is the same as found in a Li- ion battery. The positive electrode uses the nitroxide - oxammonium cation redox pair to create an electrochemical potential, i.e. when the battery discharges the nitroxide radical is oxidized to the oxammonium cation and when the battery charges the oxammonium cation is reduced back to the nitroxide. The redox potentials for nitroxide show some variation and for the TEMPO nitroxide for this redox pair has an oxidation potential of +0.87 V. The positive electrode often takes the shape of a gel made of organic radical solids and graphite, permeated with electrolytes.
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For example, the amphibole group consists of 15 or more mineral species, most of them with the general unit formula , where A is a trivalent cation such as or , B is a divalent cation such as , , or , and C is an alkali metal cation such as , , or . In all these minerals, the anions consist mainly of groups of four tetrahedra connected by shared oxygen corners so as to form a double chain of fused six-member rings. In some of the species, aluminum may replace some silicon atoms in the backbone, with extra B or C cations to balance the charges.
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Solute carrier family 22 member 3 (SLC22A3) also known as the organic cation transporter 3 (OCT3) or extraneuronal monoamine transporter (EMT) is a protein that in humans is encoded by the SLC22A3 gene. Polyspecific organic cation transporters in the liver, kidney, intestine, and other organs are critical for elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. This gene is one of three similar cation transporter genes located in a cluster on chromosome 6. The encoded protein contains twelve putative transmembrane domains and is a plasma integral membrane protein.
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Some carbocations such as the 2-norbornyl cation exhibit more or less symmetrical three-center two- electron bonding. Such structures, referred to as non-classical carbocations, involve the delocalization of the bonds involved in the σ-framework of the molecule and the drawing of "no-bond" resonance forms (beyond the relatively simple variety encountered in hyperconjugation). As circumstantial evidence of its unusual bonding, the 2-norbornyl cation is also more stable than a typical "secondary" carbocation, being roughly as stable as t-butyl cation, according to hydride ion affinity. The existence of non-classical carbocations was once the subject of great controversy.
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Similarly the cation of the electrolyte should be of the same metal as well. When the current source is turned on, the metal of the anode is dissolved and converted into the same cation as in the electrolyte and at the same time an equal amount of the cation in the solution is converted into metal and deposited on the cathode. Depending on the voltage used and the concentration of the electrolyte, other, more complex electrochemical effects can take place at the anode and the cathode but the solution at the anode and deposition at the cathode are the main effects.
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Saul Winstein (October 8, 1912 - November 23, 1969) was a Jewish Canadian chemist who discovered the Winstein reaction. He argued a non-classical cation was needed to explain the stability of the norbornyl cation. This fueled a debate with Herbert C. Brown over the existence of σ-delocalized carbocations. Winstein also first proposed the concept of an intimate ion pair.
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In the first step, the binding step, the carboxylate group changes from the axial position into the pseudo-equatorial position. The second step is the proton donation from water molecule and formation of the endocyclic sialosyl cation transition-state intermediate. Step three involves nucleophilic attack of tyrosine on the sialosyl cation. The fourth step is the formation and release of Neu5Ac.
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Olaflur is a salt consisting of an alkyl ammonium cation and fluoride as the counterion. With a long lipophilic hydrocarbon chain, the cation has surfactant properties. It forms a film layer on the surface of teeth, which facilitates incorporation of fluoride into the enamel. The top layers of the enamel's primary mineral, hydroxylapatite, are converted into the more robust fluorapatite.
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If the substance lacks the ability to dissolve in water, the molecules form a precipitate. Reactions in aqueous solutions are usually metathesis reactions. Metathesis reactions are another term for double-displacement; that is, when a cation displaces to form an ionic bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion.
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Electrical conductivity variations include cation and anion conductivity. Chromatography such as ion chromatography or HPLC often tests the output stream continuously by measuring electrical conductivity, particularly cation or anion conductivity, refractive index, colorimetry or ultraviolet/visible absorbance at a certain wavelength. InlineOnline and offline analysers are available for other types of analytes. Many of these add reagents to the samples or sample streams.
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Sodium is the primary cation (positive ion) in extracellular fluids in animals and humans. These fluids, such as blood plasma and extracellular fluids in other tissues, bathe cells and carry out transport functions for nutrients and wastes. Sodium is also the principal cation in seawater, although the concentration there is about 3.8 times what it is normally in extracellular body fluids.
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The cis form of dinitrogen difluoride will react with strong fluoride ion acceptors such as antimony pentafluoride to form the N2F+ cation. : N2F2 \+ SbF5 → N2F+[SbF6]− In the solid phase, the observed N=N and N−F bond distances in the N2F+ cation are 1.089(9) and 1.257(8) Å respectively, among the shortest experimentally observed N−N and N−F bonds.
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For type-I ionic binary compounds, the cation (a metal in most cases) is named first, and the anion (usually a nonmetal) is named second. The cation retains its elemental name (e.g., iron or zinc), but the suffix of the nonmetal changes to -ide. For example, the compound LiBr is made of Li+ cations and Br− anions; thus, it's called lithium bromide.
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Ferrous oxide is more correctly called iron(II) oxide. In chemistry, the adjective ferrous indicates a compound that contains iron in the +2 oxidation state, possibly as the divalent cation Fe2+. It is opposed to "ferric", which indicates presence of iron in a +3 oxidation state, such as the trivalent cation Fe3+."ferrous" entry in the Merriam-Webster online dictionary.
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Information obtained on the nature of ions in solution varies with the nature of the experimental method used. Some methods reveal properties of the cation directly, others reveal properties that depend on both cation and anion. Some methods supply information of a static nature, a kind of snapshot of average properties, others give information about the dynamics of the solution.
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Transient receptor potential cation channel, subfamily M, member 7, also known as TRPM7, is a human gene encoding a protein of the same name.
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Transient receptor potential cation channel, subfamily C, member 7, also known as TRPC7, is a human gene encoding a protein of the same name.
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Because telluropyrylium is a positively charged cation, it takes the solid form as a salt with non-nucleophillic anions like perchlorate, tetrafluoroborate, or hexafluorophosphate.
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Hydron is a generic term for hydrogen cation; protons, deuterons and tritons are all hydrons. The Hydrons are not found in heavier isotopes, however.
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S-adenosyl methionine. Beyond its role in cocaine, the N-methyl-pyrrolinium cation is a precursor to nicotine, hygrine, cuscohygrine, and other natural products.
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Multiple alignments contain two highly conserved aspartates that may be involved in cation binding. Human transporters from this family are SLC41A1, SLC41A2 and SLC41A3.
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A.66.9) The Progressive Ankylosis (Ank) Family All functionally characterized members of the MOP superfamily catalyze efflux of their substrates, presumably by cation antiport.
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Different analytes involve different ionization mechanisms in FD-MS, and four mechanisms are commonly observed, including field ionization, cation attachment, thermal ionization, and proton abstraction.
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Transient receptor potential cation channel, subfamily M, member 2, also known as TRPM2, is a protein that in humans is encoded by the TRPM2 gene.
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A krypton-nitrogen bond is found in the cation [HC≡N–Kr–F], produced by the reaction of with [HC≡NH][AsF] below −50 °C.
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Pyridinium refers to the cation [C5H5NH]+. It is the conjugate acid of pyridine. Many related cations are known involving substituted pyridines, e.g. picolines, lutidines, collidines.
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Because selenopyrylium is a positively charged cation, it takes the solid form as a salt with non-nucleophillic anions like perchlorate, tetrafluoroborate, fluorosulfate, or hexafluorophosphate.
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Solute carrier family 9, subfamily B (NHA2, cation proton antiporter 2), member 2 is a protein that in humans is encoded by the SLC9B2 gene.
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Ammonium azide is ionic. Ammonium azide contains about 93% nitrogen by weight as ammonium cation and azide anion. It is a structural isomer of tetrazene.
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Three consecutive amino acid residues form an anion-binding concavity. ; Niche: Extremely common. Three or four consecutive amino acid residues form a cation-binding feature.
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Streetsweepers is a mixtape record label run by DJ Kay Slay that launched the careers of Amerie, Saigon, Grafh, Prinz, Thug-A-Cation, and Papoose.
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Because Ti(IV) is a "hard cation", the sulfides of titanium are unstable and tend to hydrolyze to the oxide with release of hydrogen sulfide.
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Additional helium atoms can attach to HeH+ to form larger clusters such as He2H+, He3H+, He4H+, He5H+ and He6H+. The dihelium hydride cation, He2H+, is formed by the reaction of dihelium cation with molecular hydrogen: : + H2 → He2H+ \+ H It is a linear ion with hydrogen in the centre. The hexahelium hydride ion, He6H+, is particularly stable. Other helium hydride ions are known or have been studied theoretically.
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The lone electron pair on the nitrogen atom (N) in ammonia, represented as a line above the N, forms the bond with a proton (H+). Thereafter, all four N–H bonds are equivalent, being polar covalent bonds. The ion has a tetrahedral structure and is isoelectronic with methane and borohydride. In terms of size, the ammonium cation (rionic = 175 pm) resembles the caesium cation (rionic = 183 pm).
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In the first stage of the reaction the pernigraniline PS salt oxidation state is formed. In the second stage pernigraniline is reduced to the emeraldine salt as aniline monomer gets oxidized to the radical cation. In the third stage this radical cation couples with ES salt. This process can be followed by light scattering analysis which allows the determination of the absolute molar mass.
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The 10+ cation would satisfy this rule, and should be aromatic. This has been shown to be the case using quantum chemical modelling, which showed the existence of strong diamagnetic sphere currents in the cation. As a result, in water tends to pick up two more electrons and become an anion. The n described below may be the result of trying to form a loose metallic bond.
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The cyclic pentazolium cation () is not known due to its probable antiaromatic character; whereas the open-chained pentazenium cation () is known. Butler et al. first demonstrated the presence of the cyclic in solution through the decomposition of substituted aryl pentazoles at low temperature. The presence of and (held in solution through the interaction with zinc ions) was proven primarily using 15N NMR techniques of the decomposition products.
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This will deprotonate water, form a tetrahedral intermediate at the original ester, and create an imidazolium cation at histidine. The final step is beta-elimination. With a newly formed imidazolium cation ready to be an acid, aspartate 124 reverts to its original acidic state and breaks the ester linkage, as well as deprotonating histidine 289. The alcohol is eliminated and the halogen is now a free anion.
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Intermediate 2 then reacts via a tautomerism and dehydration to the aryldiazonium cation 3. Dritter Teil des Reaktionsmechanismus der Pschorr-Cyclisierung Nitrogen is then cleaved from the aryldiazonium cation 3 by the use of the copper catalyst. The aryl radical thus formed reacts via ring closure to the intermediate stage 4. Finally, rearomatization takes place using again the copper catalyst and phenanthrene is formed.
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Acid salt is an ionic compound consisted of an anion, contributed from a weak parent acid, and a cation, contributed from a strong parent base. Research says that ics + ics= 2ics and between the anion and cation ics, the result gives guys. An example, for instance, is tetraoxidosulfate(2-). We write it as 2- because we do not know how to write in math.
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Renal handling of potassium is closely connected to sodium handling. Potassium is the major cation (positive ion) inside animal cells [150mmol/L, (4.8g)], while sodium is the major cation of extracellular fluid [150mmol/L, (3.345g)]. In the kidneys, about 180liters of plasma is filtered through the glomeruli and into the renal tubules per day. This filtering involves about 600g of sodium and 33g of potassium.
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The ATP-gated P2X receptor cation channel family (TC# 1.A.7), or simply P2X receptor family, consists of cation-permeable ligand-gated ion channels that open in response to the binding of extracellular adenosine 5'-triphosphate (ATP). They belong to a larger family of receptors known as the ENaC/P2X superfamily. ENaC and P2X receptors have similar 3-D structures and are homologous.
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By treating this compound with an alkaline solution of hypochlorite, C6H5AtO2 can be produced. The dipyridine-astatine(I) cation, [At(C5H5N)2]+, forms ionic compounds with perchlorate (a non-coordinating anion) and with nitrate, [At(C5H5N)2]NO3. This cation exists as a coordination complex in which two dative covalent bonds separately link the astatine(I) centre with each of the pyridine rings via their nitrogen atoms.
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Other tests measure the antioxidant capacity of a fraction. Some make use of the ABTS radical cation which is reactive towards most antioxidants including phenolics, thiols and vitamin C. During this reaction, the blue ABTS radical cation is converted back to its colorless neutral form. The reaction may be monitored spectrophotometrically. This assay is often referred to as the Trolox equivalent antioxidant capacity (TEAC) assay.
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This gene encodes a member of the organic- cation transporter family. It is located in a gene cluster with another member of the family, organic cation transporter like 4. The encoded protein is a transmembrane protein involved in the transport of small molecules. This protein can function to mediate urate uptake and is a high affinity nicotinate exchanger in the kidneys and the intestine.
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The homotropylium cation, (C8H9+), though not the first example of a homoaromatic compound ever discovered, has proven to be the most studied of the compounds classified as homoaromatic, and is therefore often considered the classic example of homoaromaticity. By the mid-1980s, there were more than 40 reported substituted derivatives of the homotropylium cation, reflecting the importance of this ion in formulating our understanding of homoaromatic compounds.
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The origin of substituent effects in cation–π interactions has often been attributed to polarization from electron donation or withdrawal into or out of the π system. This explanation makes intuitive sense, but subsequent studies have indicated that it is flawed. Recent computational work by Wheeler and Houk strongly indicate that the effect is primarily due to direct through-space interaction between the cation and the substituent dipole. In this study, calculations that modeled unsubstituted benzene plus interaction with a molecule of "H-X" situated where a substituent would be (corrected for extra hydrogen atoms) accounted for almost all of the cation–π binding trend.
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The nature of bonding in the 2-norbornyl cation was the center of a vigorous, well-known debate in the chemistry community through the middle of the twentieth century. While the majority of chemists believed that a three-center two-electron bond best depicted its ground state electronic structure, others argued that all data concerning the 2-norbornyl cation could be explained by depicting it as a rapidly equilibrating pair of cations. At the height of the debate, all chemists agreed that the delocalized picture of electron bonding could be applied to the 2-norbornyl cation. But this did not answer the fundamental question on which the debate hinged.
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Figure 9: Decomposition of isotopically labeled 2-norbornyl cation. Radioactive isotope labeling experiments provide a powerful tool for determining the structure of organic molecules. By systematically decomposing the 2-norbornyl cation and analyzing the amount of radioactive isotope in each decomposition product, researchers were able to show further evidence for the non-classical picture of delocalized bonding (see Figure 9). Proponents of the nonclassical picture would expect 50% of the generated CO2 in the decomposition in Figure 9 to contain 14C, while proponents of the classical picture would expect more of the generated CO2 to be radioactive due to the short-lived nature of the cation.
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Ion exchange chromatography is often employed in the first step, or capturing step, for the separation of PEGylated proteins as PEGylation may affect the charges of target proteins by neutralizing electrostatic interaction, changing the isoelectric point (pI), and increasing the pKa value. Due to the high pI of lysozyme (pI = 10.7), cation exchange chromatography is used. As the increased degree of PEGylation decreases the ion strength of the protein, the poly-PEGylated proteins tend to bind to the cation resin weaker than the mono-PEGylated protein or the intact form does. Thus, the poly-PEGylated proteins elute faster and the intact protein eludes last in the cation exchange chromatography.
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Toth, in a later experiment to investigate the 'ideal soil' ratios he had previously worked on with Bear, came to the conclusion that so long as calcium was the dominant cation, no specific cation ratio produced a better yield of ladino clover.Giddens, J. and Toth. 1951. Growth and nutrient uptake of ladino clover on red and yellow grey-brown podzolic soils Even with Mg and K as high as 40%, far higher than the 'ideal' range, no difference in yield was obtained. Similar conclusions have since been drawn by other studies showing no relation between yield and cation ratios, providing calcium is more abundant than magnesium.McLean, E.O. and Carbonell. 1972.
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In these reactions, a positive electrophile attacks one of the unsaturated carbons that then forms a vinyl cation, which subsequently undergoes further reaction steps to form the final product. In the acid-catalyzed hydration of arylacetylene derivatives, a proton initially attacks the triple bond to form a vinyl cation at the aryl substituted carbon. The intermediate experiences little resonance stabilization because of the orthogonality of the conjugated aryl orbital with the empty p-orbital of the vinyl cation. The reaction is first order with respect to both the acetylene and the proton and with the protonation of the acetylene as the rate-determining step.
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Cyclization of geranyl diphosphate into (+)- bornyl diphosphate synthase catalyzed by Bornyl Diphosphate Synthase As seen in the mechanism above, bornyl diphosphate synthase catalyzes the cyclization cascade of GPP into (+)- bornyl diphosphate. Following the initial metal-activated diphosphate departure from GPP, the molecule isomerizes to linalyl diphosphate (LPP), which then allows for the rotation around the carbon-carbon bond, and consequent reattachment of the PPi group. The pyrophosphate then stabilizes the cyclization into the terpinyl cation, and another final cyclization yields the 2-bornyl cation. This cation is then neutralized by the stereo-specific C–O bond formation with the final re-attachment of pyrophosphate to create the final product, BPP.
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Sodium is usually the first ion to break through a depleted cation exchanger. Sodium measurement can quickly detect this condition and is widely used as the indicator for cation exchange regeneration. The conductivity of cation exchange effluent is always quite high due to the presence of anions and hydrogen ion and therefore conductivity measurement is not useful for this purpose. Sodium is also measured in power plant water and steam samples because it is a common corrosive contaminant and can be detected at very low concentrations in the presence of higher amounts of ammonia and/or amine treatment which have a relatively high background conductivity.
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The salt consists of a protonated tryptammonium cation and a 3-carboxyacrylate (hydrogen fumarate) anion in the asymmetric unit along with a water molecule of crystallization.
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Cycloheptatriene is not aromatic, as reflected by the nonplanarity of the methylene bridge (-CH2-) with respect to the other atoms; however the related tropylium cation is.
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When substitution of Al3+ for Si4+ creates a charge imbalance, an interlayer cation will fill in between tetrahedral layers to balance the charge of the clay.
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Reverse weathering generally refers to the formation of a clay neoformation that utilizes cations and alkalinity in a process unrelated to the weathering of silicates. More specifically reverse weathering refers to the formation of authigenic clay minerals from the reaction of 1) biogenic silica with aqueous cations or cation bearing oxides or 2) cation poor precursor clays with dissolved cations or cation bearing oxides. Formation of cation abundant authigenic silicate clays is thought to occur through the following simplified reaction: > Biogenic opal (SiO2) + metal hydroxides (Al(OH)4−) + dissolved cations (K+, > Mg2+, Li+, etc.) + bicarbonate (HCO3) → clay minerals + H2O + CO2 The formation of authigenic clay minerals by reverse weathering is not fully understood. Much of the research done has been conducted in localized areas, such as the Amazon delta, Mississippi delta, and in the Ethiopian Rift lakes, making a global understanding of the process difficult.
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Several criteria influence the strength of the bonding: the nature of the cation, solvation effects, the nature of the π system, and the geometry of the interaction.
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Transient receptor potential cation channel subfamily M member 4 (hTRPM4), also known as melastatin-4, is a protein that in humans is encoded by the TRPM4 gene.
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This protein is 57% identical, 10% similar to ChR1. It forms a cation-selective ion channel activated by light absorption. It transports both monovalent and divalent cations.
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Both a cation and a dication are known. The dication HB2− can be a ligand with two links. The dication can also be stabilized by an amine.
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Selectivity of crystalline membranes can be for both cation and anion of the membrane-forming substance. An example is the fluoride selective electrode based on LaF3 crystals.
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Solute carrier family 12 member 8 (SLC12A8), also known as cation-chloride cotransporter 9 (CCC9), is a protein that in humans is encoded by the SLC12A8 gene.
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The former method is preferred commercially. However, as commercial manufacturers are reluctant to share their procedures, little is known about the exact conditions of the melt-mixing neutralization process other than that hydroxides are generally used to provide the metal cation. The latter solution neutralization process is generally used in academic settings. The acid copolymer is dissolved and a basic salt with the appropriate metal cation is added to this solution.
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Molybdenum is a transition metal with an electronegativity of 2.16 on the Pauling scale. It does not visibly react with oxygen or water at room temperature. Weak oxidation of molybdenum starts at ; bulk oxidation occurs at temperatures above 600 °C, resulting in molybdenum trioxide. Like many heavier transition metals, molybdenum shows little inclination to form a cation in aqueous solution, although the Mo3+ cation is known under carefully controlled conditions.
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Carboxylation of adamantane was first reported in 1960, using formic acid as a carboxylating agent and carbon tetrachloride as a solvent. 500px tert-butanol (t-BuOH) and sulfuric acid were added to generate adamantane cation; the cation was then carboxylated by carbon monoxide generated in situ in the interaction between the formic and sulfuric acids. The fraction of carboxylated adamantane was 55-60%.1-Adamantanecarboxylic acid Organic Syntheses, Coll. Vol.
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The mechanism of the Nicholas reaction The addition of dicobalt octacarbonyl to a propargylic ether (1) gives the dicobalt intermediate 2. Reaction with HBF4 or Lewis acid gives the key dicobalt octacarbonyl-stabilized propargylic cation (3a and 3b). Addition of a nucleophile followed by a mild oxidation gives the desired substituted alkyne (5). The likely intermediates in the reactions, [(propargylium)Co2(CO)6]+ cation 3, possessed considerable stability.
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Some organic minerals do not fall into the above categories. These include nickel porphyrin (), closely related to biological molecules such as heme (a porphyrin with iron as the cation) and chlorophyll (a magnesium cation), but does not itself occur in biological systems. Instead, it is found on the surface of fractures in oil shales. Urea derived from bat guano and urine also occurs as a mineral in very arid conditions.
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Thermodynamic and kinetic controlled products of hydrohalogenation of alkynes through vinyl cation intermediate. Adapted from In the hydrohalogenation of phenylpropene, two different alkene products are formed because of thermodynamic and kinetic effects. The linear sp-hybridized vinyl cation may be attacked by the halogen from two different directions. When attacked from the less sterically hindered side (hydrogen), the E-alkene is produced, attack to the other side forms the Z-alkene.
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Major types of rearrangements in vinyl cations. Adapted from Vinyl cations intermediates that are formed during reactions can have a tendency to undergo rearrangements. These rearrangements can be broadly categorized into two classes: migrations into double bonds and rearrangements via the double bonds. The first category involves 1,2-shifts that lead to the formation of an allyl cation, while the second type involves the formation of another vinyl cation isomer.
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In most cases, an excess of the diene is employed to prevent isomerization of the oxyallyl cation intermediate. Increasing the covalent character of the metal-oxygen bond (by, for instance, employing iron carbonyl reducing agents instead of sodium) also stabilizes the oxyallyl cation, leading to cleaner reactions. Strongly electrophilic allyl cations tend to give products of electrophilic substitution rather than cycloaddition.Henning, R.; Hoffmann, H. M. R. Tetrahedron Lett.
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Chemical stimuli, such as odorants, are received by cellular receptors that are often coupled to ion channels responsible for chemotransduction. Such is the case in olfactory cells. Depolarization in these cells result from opening of non-selective cation channels upon binding of the odorant to the specific receptor. G protein-coupled receptors in the plasma membrane of these cells can initiate second messenger pathways that cause cation channels to open.
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Anthranilic acid can be diazotized to give the diazonium cation [C6H4(CO2H)(N2)]+. This cation can be used to generate benzyne, dimerized to give diphenic acid, or undergo diazonium coupling reactions such as in the synthesis of methyl red. It reacts with phosgene to give isatoic anhydride, a versatile reagent. Chlorination of anthranilic acid gives the 2,4-dichloro derivative, which can undergo reductive coupling to form a biaryl compound.
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This process is called AdE2 mechanism ("addition, electrophilic, second-order"). Iodine (I2), chlorine (Cl2), sulfenyl ion (RS+), mercury cation (Hg2+), and dichlorocarbene (:CCl2) also react through similar pathways. The direct conversion of 1 to 3 will appear when the Br− is large excess in the reaction medium. A β-bromo carbenium ion intermediate may be predominant instead of 3 if the alkene has a cation-stabilizing substituent like phenyl group.
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The high affinity of 18-crown-6 for potassium ions contributes to its toxicity. The smallest crown ether still capable of binding cations is 8-crown-4, with the largest, experimentally confirmed crown ether being 81-crown-27. Crown ethers are not the only macrocyclic ligands that have affinity for the potassium cation. Ionophores such as valinomycin also display a marked preference for the potassium cation over other cations.
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When hydrated aluminium nitrate reacts with dinitrogen pentoxide it forms a nitronium salt: [NO2]+[Al(NO3)4]−. A way to make a tetranitratoaluminate salt of a cation is to treat the chloride of the cation and aluminium chloride with liquid dinitrogen tetroxide pure or dissolved in nitromethane. The reaction is started a liquid nitrogen temperatures and then warmed up. Dark red nitrosyl chloride is formed as a byproduct.
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This enzyme participates in biosynthesis of L-leucine and pyruvate metabolism. Monovalent and divalent cation activation have been reported for enzymes from different sources. Mycobacterium tuberculosis α-isopropylmalate synthase requires a divalent metal ion, of which Mg2+ and Mn2+ give highest activity, and a monovalent cation, with K+ as the best activator. Zn2+ was shown to be an inhibitor, contrary to what was assumed from the structural data.
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This gene encodes a member of the organic- cation transporter family. It is located in a gene cluster with another member of the family, organic cation transporter like 3. The encoded protein is a transmembrane protein which is thought to transport small molecules and since this protein is conserved among several species, it is suggested to have a fundamental role in mammalian systems. Alternative splicing results in multiple transcript variants.
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The sharing of edges and particularly faces by two anion polyhedra decreases the stability of an ionic structure. Sharing of corners does not decrease stability as much, so (for example) octahedra may share corners with one another.Pauling (1960) p.559 The decrease in stability is due to the fact that sharing edges and faces places cations in closer proximity to each other, so that cation-cation electrostatic repulsion is increased.
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Calcium nitrate has a similar effect, with NaNO3 in the leachate. Spent acid (HCl, H2SO4, etc.) can also be used to reduce the excess Na2CO3 in the soil/water. Where urea is made available cheaply to farmers, it is also used to reduce the soil alkalinity / salinity primarily. The NH4 (Ammonium) present in urea which is a weak cation releases the strong cation Na from the soil structure into water.
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Members of the Non-Selective Cation Channel-2 (NSCC2) Family (TC#1.A.15) have been sequenced from various yeast, fungal and animals species including Saccharomyces cerevisiae, Drosophila melanogaster and Homo sapiens. These proteins are the Sec62 proteins, believed to be associated with the Sec61 and Sec63 constituents of the general protein secretory systems of yeast microsomes. They are also the non-selective (NS) cation channels of the mammalian cytoplasmic membrane.
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In general, potassium binders are artificial resins that exchange bound cations (Ca2+ or Na+) for potassium ions in the large intestine. After exchange, the released cation and potassium adhering to the resin are excreted with the faeces. This mechanism prevents intestinal absorption of alimentary potassium ions and thereby reduces serum potassium levels. There are two major classes of binders, differentiated by the cation attached to the resin in the original condition.
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With fully solvated and solvent-shared ion pairs the interaction is primarily electrostatic, but in a contact ion pair some covalent character in the bond between cation and anion is also present. An ion triplet may be formed from one cation and two anions or from one anion and two cations. Higher aggregates, such as a tetramer (AB)4, may be formed. Ternary ion associates involve the association of three species.
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In general, complex metal hydrides have the formula MxM'yHn, where M is an alkali metal cation or cation complex and M' is a metal or metalloid. Well known examples feature group 13 elements, especially boron and aluminium including sodium aluminium hydride, NaAlH4 (also known as sodium alanate), lithium aluminum hydride, LiAlH4, and lithium borohydride, (LiBH4). Complex metal hydrides are often soluble in etherial solvents. Other complex metal hydrides are numerous.
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One of the chemical names for the compound is lidocaine benzylbenzoate, although denatonium only denotes the quaternary ammonium cation species itself, and does not necessitate the benzoate counterion.
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As mono-PEGylated is widely investigated and described as a protection of target proteins, the target eluate in the cation exchange chromatography is usually the mono-PEGylated proteins.
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Solute carrier family 22 (organic anion/cation transporter), member 12, also known as SLC22A12 and URAT1, is a protein which in humans is encoded by the SLC22A12 gene.
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Finally, four symmetrical cation binding sites in the extracellular vestibule mediate the recruitment of cations towards the extracellular vestibule of TRPV6 and are referred to as recruitment sites.
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There is a possibility to use calcium sulfite to produce gypsum by oxidizing (adding O2) it in water mixture with the manganese (Mn2+) cation or sulfuric acid catalyzers.
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Olah, with Canadian chemist Saul Winstein, was also involved in a career-long battle with Herbert C. Brown of Purdue over the existence of so-called "nonclassical" carbocations – such as the norbornyl cation, which can be depicted as cationic character delocalized over several bonds. Olah's studies of the cation with NMR spectroscopy provided more evidence suggesting that Winstein's model of the non-classical cation, "featuring a pair of [delocalized] electrons smeared between three carbon atoms," was correct. In 1997, the Olah family formed an endowment fund (the George A. Olah Endowment) which grants annual awards to outstanding chemists, including the George A. Olah Award in Hydrocarbon or Petroleum Chemistry, formerly known as the ACS Award in Petroleum Chemistry.
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The 2-norbornyl cation can also be formed via rearrangements of similar ions, such as the 1-norbornyl and 7-norbornyl cations, though these are generally not as well understood. Carbon-14 radioactive isotope labeling experiments have shown that complex scrambling in norbornyl cation systems allow C to be present at all seven positions of the norbornyl system. By cycling between low and high temperatures during the hydrolyses of 1- and 7-choloronorbornanes, a large amount of 2-norbornanol was observed in addition to the expected 1- and 7-norbornanols, respectively. Thus the 1- and 7-norbornyl cations have some mechanism by which they can rearrange to the more stable 2-norbornyl cation on the timescale of solvolysis reactions.
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For molecules in dynamic equilibrium such as the 2-norbornyl cation, nuclei within each set can also be transformed to one another through rearrangements with fast reaction rates. Since the proposed dynamic equilibrium of the classical ion proponents had very fast rates of rearrangement, the first NMR studies did not favor nor invalidate any of the three proposed structures. But by using solid-state NMR analysis, one can lower the temperature of the NMR experiment to and thus significantly slow down any rearrangement phenomena. Solid-state C NMR spectra of the 2-norbornyl cation shows that carbons 1 and 2 are in identical chemical environments, which is consistent only with the non-classical picture of the 2-norbornyl cation.
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Inverse spinel structures have a different cation distribution in that all of the A cations and half of the B cations occupy octahedral sites, while the other half of the B cations occupy tetrahedral sites. An example of an inverse spinel is Fe3O4, if the Fe2+ (A2+) ions are d6 high-spin and the Fe3+ (B3+) ions are d5 high-spin. In addition, intermediate cases exist where the cation distribution can be described as (A1−xBx)[AB1−]2O4, where parentheses () and brackets [] are used to denote tetrahedral and octahedral sites, respectively. The so-called inversion degree, x, adopts values between 0 (normal) and 1 (inverse), and is equal to for a completely random cation distribution.
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When using Kröger–Vink notation for both intrinsic and extrinsic defects, it is imperative to keep all masses, sites, and charges balanced in each reaction. If any piece is unbalanced, the reactants and the products do not equal the same entity and therefore all quantities are not conserved as they should be. The first step in this process is determining the correct type of defect and reaction that comes along with it; Schottky and Frenkel defects begin with a null reactant (∅) and produce either cation and anion vacancies (Schottky) or cation/anion vacancies and interstitials (Frenkel). Otherwise, a compound is broken down into its respective cation and anion parts for the process to begin on each lattice.
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Comparison between a molybdenum-complex and an iron-complex proved particularly fruitful. Molybdenum tricarbonyl was expected to coordinate to the homotropylium cation by accepting 6 π electrons, thereby preserving the homoaromatic features of the complex. By contrast, iron tricarbonyl was expected to coordinate to the cation by accepting only 4 π electrons from the homotropylium ion, creating a complex in which the electrons of the cation are localized. Studies of these complexes by 1H NMR spectroscopy showed a large difference in chemical shift values for methylene protons of the Mo-complex, consistent with a homoaromatic structure, but detected virtually no comparable difference in resonance for the same protons in the Fe-complex.
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The extent of this type of ion pairing decreases as the size of the cation increases. Thus, solvent-shared ion pairs are characterized by a rather small shift of vibration frequency with respect to the "free" solvated anion, and the value of the shift is not strongly dependent on the nature of the cation. The shift for contact ion pairs is, by contrast, strongly dependent on the nature of the cation and decreases linearly with the ratio of the cations charge to the squared radius: :Cs+ > Rb+ > K+ > Na+ > Li+; :Ba2+ > Sr2+ > Ca2+. The extent of contact ion pairing can be estimated from the relative intensities of the bands due to the ion pair and free ion.
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Tibezonium iodide (or tibenzonium iodide) is an antiseptic for use in the mouth. It is a salt consisting of a lipophilic quaternary ammonium cation and iodide as the counterion.
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A similar variation was observed for the M2PaF7 fluorides, namely the crystal symmetry was dependent on the cation and differed for Cs2PaF7 and M2PaF7 (M = K, Rb or NH4).
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Spinels are grouped in series by the B cation. Though spinels are often referred to as rubies, as in the Black Prince Ruby, the ruby is not a spinel.
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Ascorbic acid Mineral ascorbates are a group of salts of ascorbic acid (vitamin C). They are composed of a mineral cation bonded to ascorbate (the anion of ascorbic acid).
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The latter compound is stable at but begins to decompose at . Additionally, the pentamethylcyclopentadienylsilicon(II) cation can react with metal precursors to generate complexes with metal-silicon multiple bonds.
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Double sulfates of the composition , where A is a univalent cation and B is a divalent metal ion are referred to as langbeinites, after the prototypical potassium magnesium sulfate.
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Basic Red 18 is a cationic azo dye used for coloring textiles. The chromophore is the cation, which contains many functional groups, but most prominently the quaternary ammonium center. It is produced by azo coupling of 2-chloro-4-nitrophenyldiazonium cation with the quaternary ammonium salt derived from N-ethyl-N-(2-chloroethyl)aniline and trimethylamine.. Like many dyes, methods for the removal of Basic Red 18 from waste streams has received much attention.
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A combination of anion-binding and cation- pi strategies can be used to effect enantioselective cationic polycyclizations. In the transition state, it is proposed that the thiourea group binds chloride, while the aromatic system stabilizes the associated polyene cation. In support of this, increasing the size of the aromatic ring leads to improvements both in yield and stereoselectivity. The enantioselectivity correlates well with both the polarizability and the quadrupole moment of the aryl group.
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Different methods can be used to synthesize PPy, but the most common are electrochemical synthesis and chemical oxidation. Chemical oxidation of pyrrole: :n C4H2NH + 2n FeCl3 → (C4H2NH)n \+ 2n FeCl2 \+ 2n HCl The process is thought to occur via the formation of the pi-radical cation C4H4NH+. This electrophile attacks the C-2 carbon of an unoxidized molecule of pyrrole to give a dimeric cation [(C4H4NH)2]++. The process repeats itself many times.
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The positively charged species (e.g., sodium) in the D stream migrate toward the negatively charged cathode and pass through the negatively charged cation exchange membrane. These cations also stay in the C stream, prevented from further migration toward the cathode by the positively charged anion exchange membrane.AWWA, Electrodialysis and Electrodialysis Reversal, American Water Works Association, Denver (1995) As a result of the anion and cation migration, electric current flows between the cathode and anode.
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Thus, the cyclobutyl cation may actually be a transition state between the two cyclopropylcarbinyl cations, rather than a discrete intermediate. The stereochemistry of the intermediates and the olefin geometry in the final product is dictated by the suprafacial nature of the 1,2-shifts and stereoelectronic requirements. While other mechanisms have been proposed, the mechanism shown above is supported by isolation of rillingol, which is the alcohol formed from trapping the second cyclopropylcarbinyl cation with water.
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SGK1 is upregulated by osmotic and isotonic cell shrinkage. "It is tempting to speculate that SGK1-dependent regulation of cation channels contributes to the regulation of cell volume, which involves cation channels in a variety of cells". The entrance of NaCl and osmotically driven water into cells leads to an increase in the cell's regulatory cell volume. This occurs as the entrance of Na+ depolarizes the cell, thus allowing the parallel entrance of Cl−.
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Thiopyrylium is a cation with the chemical formula C5H5S+. It is analogous to the pyrylium cation with the oxygen atom replaced by a sulfur atom. Thiopyrylium salts are less reactive than the analogous pyrylium salts due to the higher polarizability of the sulfur atom. Among the chalcogenic 6-membered unsaturated heterocycles, thiopyrylium is the most aromatic, due to sulfur having the similar Pauling electronegativity as carbon and only a slightly higher covalent radius.
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The tropylium cation reacts with nucleophiles to form substituted cycloheptatrienes, for example: : + → Reduction by lithium aluminum hydride yields cycloheptatriene. Reaction with a cyclopentadienide salt of sodium or lithium yields 7-cyclopentadienylcyclohepta-1,3,5-triene: : + → + When treated with oxidising agents such as chromic acid, the tropylium cation undergoes rearrangement into benzaldehyde: : + → + + Many metal complexes of tropylium ion are known. One example is [Mo(η7-C7H7)(CO)3]+, which is prepared by hydride abstraction from cycloheptatrienemolybdenum tricarbonyl.
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The bond valence method is a development of Pauling's rules. In 1930, Bragg showed that Pauling's electrostatic valence rule could be represented by electrostatic lines of force emanating from cations in proportion to the cation charge and ending on anions. The lines of force are divided equally between the bonds to the corners of the coordination polyhedron. Starting with Pauling in 1947 a correlation between cation–anion bond length and bond strength was noted.
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Aurivillius phases are a form of perovskite represented by the general formulae is (Bi2O2)(An−1BnO3n+1) (where A is a large 12 co-ordinate cation, and B is a small 6 co-ordinate cation). Basically, their structure is built by alternating layers of [Bi2O2]2+ and pseudo-perovskite blocks, with perovskite layers that are n octahedral layers in thickness. This crystal structure was first described in 1949 by B. Aurivillius.Aurivillius B., Ark. Kemi.
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The vinyl cation is a carbocation with the positive charge on an alkene carbon. Its empirical formula is . More generally, a vinylic cation is any disubstituted, trivalent carbon, where the carbon bearing the positive charge is part of a double bond and is sp hybridized. In the chemical literature, substituted vinylic cations are often referred to as vinyl cations, and understood to refer to the broad class rather than the variant alone.
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Electrodeionization installation scheme The typical RW-EDI installation has the following components: anode and cathode, anion exchange membrane, cation exchange membrane and the resin. The most simplified configuration consist in 3 compartments, to increase the production these number can be increased. The cations flow towards the cathode and the anions flows toward the anode. Only anions can go through the anion exchange membrane and only cations can go through the cation exchange membrane.
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Simple imidazolium cation Salts of imidazole where the imidazole ring is the cation are known as imidazolium salts (for example, imidazolium chloride or nitrate). These salts are formed from the protonation or substitution at nitrogen of imidazole. These salts have been used as ionic liquids and precursors to stable carbenes. Salts where a deprotonated imidazole is an anion are also well known; these salts are known as imidazolates (for example, sodium imidazolate, NaC3H3N2).
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The NMDA receptor is a non-specific cation channel that can allow the passage of Ca2+ and Na+ into the cell and K+ out of the cell. The excitatory postsynaptic potential (EPSP) produced by activation of an NMDA receptor increases the concentration of Ca2+ in the cell. The Ca2+ can in turn function as a second messenger in various signaling pathways. However, the NMDA receptor cation channel is blocked by Mg2+ at resting membrane potential.
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Alternately, one could view this structure as a face- centered cubic structure with secondary atoms in its octahedral holes. Examples of compounds with this structure include sodium chloride itself, along with almost all other alkali halides, and "many divalent metal oxides, sulfides, selenides, and tellurides". More generally, this structure is more likely to be formed if the cation is somewhat smaller than the anion (a cation/anion radius ratio of 0.414 to 0.732).
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Therefore, the following routes are possible options: (i) For M=Ln including La, Ce, Pr, Nd and Gd, unsolvated cation route is preferred since [(C5Me5)2LnH]x complexes are too reactive. 602x602px Notably, the synthesis of (C5Me5)3La and (C5Me5)3Ce requires the usage of silylated glassware since they are easily oxidized. (ii) For M=actinide like U, solvated cation route can be used. 604x604px IV. Synthesis of (C5Me5)3MZ with Z=X, H, etc.
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Haire, pp. 1584–1585 Separation of trivalent actinides from lanthanide fission products can be done by a cation-exchange resin column using a 90% water/10% ethanol solution saturated with hydrochloric acid (HCl) as eluant. It is usually followed by anion-exchange chromatography using 6 molar HCl as eluant. A cation-exchange resin column (Dowex-50 exchange column) treated with ammonium salts is then used to separate fractions containing elements 99, 100 and 101.
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Dioxygenyl hexafluoroplatinate is a compound with formula O2PtF6. It is a hexafluoroplatinate of the unusual dioxygenyl cation, O2+, and is the first known compound containing this cation. It can be produced by the reaction of dioxygen with platinum hexafluoride. The fact that is strong enough to oxidise , whose first ionization potential is 12.2 eV, led Neil Bartlett to correctly surmise that it might be able to oxidise xenon (first ionization potential 12.13 eV).
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Both Kohlrausch's law and the Debye-Hückel-Onsager equation break down as the concentration of the electrolyte increases above a certain value. The reason for this is that as concentration increases the average distance between cation and anion decreases, so that there is more inter-ionic interaction. Whether this constitutes ion association is a moot point. However, it has often been assumed that cation and anion interact to form an ion pair.
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In chemistry, a lyonium ion is the cation derived by the protonation of a solvent molecule.IUPAC Gold Book - lyonium ion For example, a hydronium ion is formed by the protonation of water, and is the cation formed by the protonation of methanol. Its counterpart is a lyate ion, the anion formed by the deprotonation of a solvent molecule. Lyonium and lyate ions, resulting from molecular autoionization, contribute to the molar conductivity of protolytic solvents.
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It is greater with the larger cations. This is counter to the trend expected if coulombic energy were the determining factor. Instead, the formation of a contact ion pair is seen to depend more on the energy needed to displace a solvent molecule from the primary solvation sphere of the cation. This energy decreases with the size of the cation, making ion pairing occur to a greater extent with the larger cations.
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In this article Faraday coins the words electrode, anode, cathode, anion, cation, electrolyte, and electrolyze. Whewell died in Cambridge in 1866 as a result of a fall from his horse.
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SLC30A1 modulates zinc permeation through the L-type calcium channel. SLC30A1 downregulates not only Zn++ influx, but also Ca++ influx, thereby protecting cells from the effects of excessive cation permeation.
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Cation, such as K+, channels are opened. III. Part III is the response of the cell. 3. An influx of Ca+ ions is activated.4. The Ca+ activates neurotransmitters. 5.
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477 Whether or not arsenic forms a cation is unclear. Its many metal alloys are mostly brittle.Eagleson 1994, p. 91 It shows fewer tendencies to anionic behaviour than ordinary nonmetals.
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The nitrosonium cation acts as the oxidizer, itself being reduced to nitric oxide gas: : M + 2NOBF4 \+ xCH3CN -> [M(CH3CN)x](BF4)2 \+ 2NO With ferrocene the ferrocenium tetrafluoroborate is formed.
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An assessment of funding allo- cation under the Job Training Partnership Act. U.S. Department of Labor, Contract No. J-9-M-5-0051. Cambridge, MA: Abt Associates. 9\. Svorny, Shirley.
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Disodium tetracarbonylferrate is the organoiron compound with the formula Na2[Fe(CO)4]. It is always used as a solvate, e.g., with tetrahydrofuran or dimethoxyethane,. which bind to the sodium cation.
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LigI from Sphingomonas is of particular interest as it has been shown to be the first member of the amidohydrolase superfamily to not require a divalent metal cation for catalytic activity.
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Transient receptor potential cation channel subfamily M member 5 (TRPM5), also known as long transient receptor potential channel 5 is a protein that in humans is encoded by the TRPM5 gene.
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Though he did not rule out the possibility of a delocalized transition state Brown continued to reject the proposed reflectional symmetry of the 2-norbornyl cation, even late in his career.
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This is RbCl's highest possible coordination number. Therefore, according to the radius ratio rule, cations in this polymorph will reach their largest apparent radius because the anion-cation distances are greatest.
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Other types of semipermeable membranes are cation exchange membrane (CEM), charge mosaic membrane (CMM), bipolar membrane (BPM), anion exchange membrane (AEM) alkali anion exchange membrane (AAEM) and proton exchange membrane (PEM).
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Prior to final filtration may be treated with a strongly acid cation exchange resin in the sodium ion form, or a weakly basic anion exchange resin in the hydroxyl ion form.
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Potassium sulfite is the inorganic compound with the formula K2SO3. It is the salt of potassium cation and sulfite anion. It is a white solid that is highly soluble in water.
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Herbert C. Brown did not believe that it was necessary to invoke a new type of bonding in stable intermediates to explain the interesting reactivity of the 2-norbornyl cation. Criticizing many chemists for disregarding past explanations of reactivity, Brown argued that all of the aforementioned information about the 2-norbornyl cation could be explained using simple steric effects present in the norbornyl system. Given that an alternative explanation using a rapidly equilibrating pair of ions for describing the 2-norbornyl cation was valid, he saw no need to invoke a stable, non-classical depiction of bonding. Invoking stable non- classical ions was becoming commonplace; Brown felt that this was not only unwarranted but also counterproductive for the field of chemistry as a whole.
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H. C. Brown, the most outspoken opponent of non-classical ions, believed that such non-classical bonding was invoked far too widely and saw no reason to deviate from the classical idea of rapidly equilibrating, discrete carbocations. In 1973, G. Olah was able to directly observe the 2-norbornyl cation by low- temperature NMR and confirm the presence of a non-classical 2-norbornyl cation, allowing the field to reach some conclusions about the possibilities of 3 center - 2 electron bonds involving carbon. This verification of delocalized sigma bonding in the 2-norbornyl system was a critical foundation for understanding hydrogen bridges between carbon atoms, another form of delocalized sigma bonding. The classical and non-classical models for bonding in the 2-norbornyl cation.
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Assume that the cation C has +1 charge and anion A has −1 charge. #Schottky defect – forming a vacancy pair on both anion and cation sites: #:∅ v + v v + v #Schottky defect (charged) – forming an electron–hole pair: #:∅ e + h #Frenkel defect – forming an interstitial and vacancy pair on an anion or cation site: #:∅ v + C v + M (cationic Frenkel defect) #:∅ v + A v + X (anionic Frenkel defect) #Associates – forming an entropically favored site, usually depending on temperature. For the two equations shown below, the right side is usually at high temperature as this allows for more movement of electrons. The left side is usually at low temperature as the electrons lose their mobility due to loss in kinetic energy.
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These cations differ with respect to the relative positions of the pair of sulfur atoms. Both isomers feature a planar ring, which is aromatic owing to the presence of 6π electrons. For example, the 1,2-ditholium ring can be represented as an allyl cation of the three carbons, with each sulfur atom donating one of its lone pairs of electrons to give a total of three pairs. Structure of diphenyl-1,2-dithiolium cation (as its bisulfate salt).
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This interaction is an example of noncovalent bonding between a monopole (cation) and a quadrupole (π system). Bonding energies are significant, with solution-phase values falling within the same order of magnitude as hydrogen bonds and salt bridges. Similar to these other non-covalent bonds, cation–π interactions play an important role in nature, particularly in protein structure, molecular recognition and enzyme catalysis. The effect has also been observed and put to use in synthetic systems.
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When coupled together, they form one molecule of geranylgeranyl diphosphate with geranylgeranyl diphosphate synthase. A molecule of GGPP generates (1) (+)-copalyl in the presence of levopimaradiene synthase. (a) Then (1) loses its OPP group catalyzed by this same synthase, performing an intramolecular allylic cyclization with the two alkenes, to form (2) the sandaracopimarenyl cation. (b) This cation then undergoes an internal cyclization to stabilize the carbocation in the ring by proton transfer to form (3) intermediate.
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The tunnel water's pH level is the lowest at the end of summer and the beginning of autumn. The most commonly occurring cation in the water of the tunnel is magnesium, which occurs in concentrations of 52 mg/l. Calcium is another cation that occurs in the tunnel water, at concentrations of 35 mg/l. Sodium and potassium also occur in the water from the Jeddo Tunnel, at concentrations of 12 and 2.2 mg/l, respectively.
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Nevertheless, also twofold degeneracies continue to be important. Among larger systems, a focus in the literature has been on benzene and its radical cation, as well as on their halo (especially fluoro) derivatives. Already in the early 1980s, a wealth of information emerged from the detailed analysis of experimental emission spectra of 1,3,5- trifluoro- and hexafluoro (and chloro) benzene radical cations. The Jahn-Teller effect in the 1,3,5-trifluoro benzene radical cation is discussed in Section 13.4.
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This and other evidence (such as NMR in superacid solutions) shows that the intermediate carbocation must have a highly delocalized structure, different from its mostly classical (delocalization exists but is small) parent molecule. This cation (an allylic cation) can be represented using resonance, as shown above. This observation of greater delocalization in less stable molecules is quite general. The excited states of conjugated dienes are stabilised more by conjugation than their ground states, causing them to become organic dyes.
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In organic chemistry, the tropylium ion or cycloheptatrienyl cation is an aromatic species with a formula of [C7H7]+. Its name derives from the molecule tropine from which cycloheptatriene (tropylidene) was first synthesized in 1881. Salts of the tropylium cation can be stable, even with nucleophiles of moderate strength e.g., tropylium tetrafluoroborate and tropylium bromide (see below). Its bromide and chloride saltsA mixture of [C7H7]+Cl− and [C7H7]+[PCl6−] is produced by treatment of tropylidene with phosphorus pentachloride.
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Although dichlorine is a strong oxidising agent with a high first ionisation energy, it may be oxidised under extreme conditions to form the cation. This is very unstable and has only been characterised by its electronic band spectrum when produced in a low-pressure discharge tube. The yellow cation is more stable and may be produced as follows:Greenwood and Earnshaw, pp. 842–44 :Cl2 \+ ClF + AsF5 This reaction is conducted in the oxidising solvent arsenic pentafluoride.
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Figure 4: In the classical depiction of the 2-norbornyl cation, there is a rapid equilibrium between two asymmetric enantiomeric structures. According to proponents of a classical double-well potential, the 2-norbornyl cation exists in dynamic equilibrium between two enantiomeric asymmetric structures. The delocalized species central to the non-classical picture is merely a transition state between the two structures. Wagner-Meerwein rearrangements are invoked as the mechanism that converts between the two enantiomers (see Figure 4).
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A hydrogen bond, as the term is used here, involves a long range interaction between hydrogen of a hydroxyl group coordinated to a cation and an oxygen atom coordinated to another cation. The reaction is predominantly electrostatic; hence an ionic bonding model is appropriate. Its axial ratio is a=0.576, b=1, c=1.6135. The hexagonal network of Si-O tetrahedra along with the superimposed layer of Al-O, OH octahedra make up the kaolin layer found in dickite.
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Vinyl cation intermediates in pericyclic reactions. Adapted from Ketenes and allenes undergo [2+2] cycloadditions under thermal conditions in a concerted manner because they have pi orbitals that are orthogonal to each other. Vinyl cation intermediates undergo the same process in the same manner because it has 2 p orbitals that can simultaneously overlap with the orbitals of the dienophile. In the Smirnov-Zamkow reaction between 2-butyne and Cl2, a cycloaddition leads to the formation of dichlorocyclobutane.
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Electrophilic attack to allene groups. Adapted from In the electrophilic attack of allenes, it takes place in a manner that prefers to form a terminal adduct and the vinyl cation at the central carbon. The polarization of the allene group show that the terminal carbons have a higher electron density and tendency to under nucleophillic attack. However, if the terminal end is stabilized by a substituent, an allyl-like cation may form as the electrophile attacks the central carbon.
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"The biosynthesis of C5-C25 terpenoid compounds". Nat. Prod. Rep. 16', 97-130 Crystal structures of recombinant tobacco 5-epi-aristolochene synthase (TEAS), alone and also complexed with two FPP analogues have been reported and analyzed to suggest the following mechanism of biosynthesis.Starks C.M.; Back K.; Chappell J.; Noel J.P.; (1997) Structural Basis for Cyclic Terpene Biosynthesis by Tobacco 5-Epi- Aristolochene Synthase. Science 277, 1815-1820 The E,E-farnesyl cation undergoes cyclization to form the germacryl cation.
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Known molecular mechanisms of cutaneous mechanosensitivity are not completely understood. Most likely, a single unifying transduction process by which all sensory neurons function does not exist. It is believed, however, that sensory neurons employ fast, mechanically gated cation channels, and that the depolarization that results across the membrane is followed by the generation of a sodium-dependent action potential at the transduction site. It is believed that rapid, mechanically gated cation channels are characteristic of all sensory neurons.
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CdIn2S4 exhibits the spinel structure, which can be described by a cubic unit cell with 8 tetrahedrally coordinated and 16 tetrahedrally coordinated cation sites. The distribution of Cd(II) and In(III) over the cation sites is difficult to elucidate from standard X-Ray Diffraction techniques because the two species are isoelectronic, but both Raman spectroscopy measurements on synthetic samples and density functional theory simulations indicate that about 20% of the tetrahedral sites are occupied by In(III) cations.
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Ion- attachment ionization is similar to chemical ionization in which a cation is attached to the analyte molecule in a reactive collision: :M + X+ + A -> MX+ + A Where M is the analyte molecule, X+ is the cation and A is a non-reacting collision partner. In a radioactive ion source, a small piece of radioactive material, for instance 63Ni or 241Am, is used to ionize a gas. This is used in ionization smoke detectors and ion mobility spectrometers.
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A steady-state plasma level of dofetilide is achieved in 2–3 days. 80% of dofetilide is excreted by the kidneys, so the dose of dofetilide should be adjusted in individuals with chronic kidney disease, based on creatinine clearance. In the kidneys, dofetilide is eliminated via cation exchange (secretion). Agents that interfere with the renal cation exchange system, such as verapamil, cimetidine, hydrochlorothiazide, itraconazole, ketoconazole, prochlorperazine, and trimethoprim should not be administered to individuals taking dofetilide.
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Antiperovskites (or inverse perovskites) is a type of crystal structure similar to the perovskite structure that is common in nature. The key difference is that the positions of the cation and anion constituents are reversed in the unit cell structure. In contrast to perovskite, antiperovskite compounds consist of two types of anions coordinated with one type of cation. Antiperovskite compounds are an important class of materials because they exhibit interesting and useful physical properties not found in perovskite materials.
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A two-coordinate approximately sp2-hybridized cation resulting from the formal removal of a hydride ion from an arene is termed an aryl cation. These carbocations are relatively unstable (aryl cations especially so) and are infrequently encountered. Hence, they are frequently omitted from introductory and intermediate level textbooks. The IUPAC definition stipulates that carbocations are even-electron species; hence, radical cations like CH4•+ that are frequently encountered in mass spectrometry are not considered to be carbocations.
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Biosynthesis begins with decarboxylation of ornithine by ornithine decarboxylase (ODC) to produce putrescine. Putrescine is then converted into N-methyl putrescine via methylation by SAM catalyzed by putrescine N-methyltransferase (PMT). N-methylputrescine then undergoes deamination into 4-methylaminobutanal by the N-methylputrescine oxidase (MPO) enzyme, 4-methylaminobutanal then spontaneously cyclize into N-methyl-Δ1-pyrrollidium cation. The final step in the synthesis of nicotine is the coupling between N-methyl-Δ1-pyrrollidium cation and niacin.
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Sodium salt are salt composed of sodium cation and the conjugate base anion of some inorganic or organic acid. They can be formed by the neutralization of the acid with sodium hydroxide.
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For example, [Cr(NH3)2Cl2Br2]− has Cr3+ as its central cation, which has a coordination number of 6 and is described as hexacoordinate. The common coordination numbers are 4, 6 and 8.
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The dianion [Fe(CO)4]2− is isoelectronic with Ni(CO)4. The iron center is tetrahedral, with Na+\---OCFe interactions. It is commonly used with dioxane complexed to the sodium cation.
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Chromium telluride (Cr2Te3) is an inorganic chemical compound. It is composed of the chromium(III) cation and the telluride anion. It has a shadowy gray color, and has a hexagonal crystal structure.
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The He(I) photoelectron spectrum of tetra-n-butylammonium iodide contains a peak at 11 eV due to the tetra-n-butylammonium cation, and at 7 and 8 eV due to iodide.
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The ionisation potential of PO is 8.39 eV. When ionised, PO forms the cation PO+. The adiabatic electron affinity of PO is 1.09 eV. On gaining an electron the PO− ion forms.
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However, the fleeting trans-C9H9+ cation, one conformation of which is shown on the right, was proposed to be a Möbius aromatic reactive intermediate in 1998 based on computational and experimental evidence.
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Polyfurans can be prepared by electrochemical approaches. The mechanism of polymerization is proposed to involve radical cation intermediates, i.e. species with the formula C4R4O+. Polyfurans can also be produced using acid catalysts.
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XRD, XAS, and IR Characterization of Copper-Exchanged Y Zeolite. The Journal of Physical Chemistry B 2000, 104, 8641. Copper cation housed within faujasite six-ring window site interacting with thiophene compound.
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Methyltriphenylphosphonium bromide is the organophosphorus compound with the formula [(C6H5)3PCH3]Br. It is the bromide salt of a phosphonium cation. It is a white salt that is soluble in polar organic solvents.
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M. F. Bechtold (1955): "Polymerization and Properties of Dilute Aqueous Silicic Acid from Cation Exchange" Journal of Physical Chemistry, volume 59, issue 6, pages 532–541. Metasilicates occur widely in nature as inosilicates.
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Other researchers found that cyclopentane derivatives that were structurally similar to the norbornyl system still featured enhanced reaction rates, leading them to claim that the classical norbornyl cation describes the system much better.
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Structures of hydrazinium and hydrazinediium . Hydrazinium is the cation with the formula . It can be derived from hydrazine by protonation (treatment with a strong acid). Hydrazinium is a weak acid with pKa = 8.1.
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9-Crown-3, also called 1,4,7-trioxonane or 1,4,7-trioxacyclononane is a crown ether with the formula C6H12O3. It is a cyclic trimer of ethylene oxide which is specific for the lithium cation.
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Electron-donating substituents lower the oxidation potential, whereas electron-withdrawing groups increase the oxidation potential. Thus, 3-methylthiophene polymerizes in acetonitrile and tetrabutylammonium tetrafluoroborate at a potential of about 1.5 V vs. SCE, whereas unsubstituted thiophene requires an additional 0.2 V. Steric hindrance resulting from branching at the α-carbon of a 3-substituted thiophene inhibits polymerization. In terms of mechanism, oxidation of the thiophene monomer produces a radical cation, which then couple with another monomer to produce a radical cation dimer.
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In 2014, researchers at Massachusetts Institute of Technology found that creating high lithium content lithium-ion batteries materials with cation disorder among the electroactive metals could achieved 660 watt-hours per kilogram at 2.5 volts. The materials of the stoichiometry Li2MO3-LiMO2 are similar to the lithium rich lithium nickel manganese cobalt oxide (NMC) materials but without the cation ordering. The extra lithium creates better diffusion pathways and eliminates high energy transition points in the structure that inhibit lithium diffusion.
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In the absence of donor ligand, lithium cation is closely coordinated to the oxygen atom, however, when the lithium cation is solvated by HMPA, the coordination between carbonyl oxygen and lithium ion is weakened. This method generally cannot be used to affect the regioselectivity of alkyl- and aryllithium reagents. :1,4vs1,2 addition Organolithium reagents can also perform enantioselective nucleophilic addition to carbonyl and its derivatives, often in the presence of chiral ligands. This reactivity is widely applied in the industrial syntheses of pharmaceutical compounds.
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The association of the cation bonding electrons with the anion in the ionic model is purely formal. There is no change in physical locations of any electrons, and there is no change in the bond valence. The terms "anion" and "cation" in the bond valence model are defined in terms of the bond topology, not the chemical properties of the atoms. This extends the scope of the ionic model well beyond compounds in which the bonding would normally be considered as "ionic".
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Biosynthesis of α-terpinene. "P" indicates a phosphate group, -PO32− The biosynthesis of α-terpinene and other terpenoids occurs via the mevalonate pathway because its starting reactant, dimethylallyl pyrophosphate (DMAPP), is derived from mevalonic acid. Geranyl pyrophosphate (GPP) is produced from the reaction of a resonance-stable allylic cation, formed from the loss of the pyrophosphate group from DMAPP, and isopentenyl pyrophosphate (IPP), and the subsequent loss of a proton. GPP then loses the pyrophosphate group to form the resonance-stable geranyl cation.
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The additional carbon atoms required for the synthesis of cocaine are derived from acetyl-CoA, by addition of two acetyl-CoA units to the N-methyl-Δ1-pyrrolinium cation. The first addition is a Mannich-like reaction with the enolate anion from acetyl-CoA acting as a nucleophile towards the pyrrolinium cation. The second addition occurs through a Claisen condensation. This produces a racemic mixture of the 2-substituted pyrrolidine, with the retention of the thioester from the Claisen condensation.
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Mannose 6-phosphate receptors (MPRs) deliver lysosomal hydrolase from the Golgi to endosomes and then return to the Golgi complex. The protein encoded by this gene interacts with the cytoplasmic domains of both cation-independent and cation-dependent MPRs, and is required for endosome-to-Golgi transport. This protein also binds directly to the GTPase RAB9 (RAB9A), a member of the RAS oncogene family. The interaction with RAB9 has been shown to increase the affinity of this protein for its cargo.
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Another model called chain ejection model (CEM) is proposed for disordered polymers (unfolded proteins). The ions observed by mass spectrometry may be quasimolecular ions created by the addition of a hydrogen cation and denoted [M + H]+, or of another cation such as sodium ion, [M + Na]+, or the removal of a hydrogen nucleus, [M − H]−. Multiply charged ions such as [M + nH]n+ are often observed. For large macromolecules, there can be many charge states, resulting in a characteristic charge state envelope.
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After initial reports of a "homoaromatic" structure for the tris-homocyclopropenyl cation were published by Winstein, many groups began to report observations of similar compounds. One of the best studied of these molecules is the homotropylium cation, the parent compound of which was first isolated as a stable salt by Pettit, et al. in 1962, when the group reacted cyclooctatraene with strong acids. Much of the early evidence for homoaromaticity comes from observations of unusual NMR properties associated with this molecule.
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The addition of a substituent to a homoaromatic compound has a large influence over the stability of the compound. Depending on the relative locations of the substituent and the homoconjugate linkage, the substituent can either have a stabilizing or destabilizing effect. This interaction is best demonstrated by looking at a substituted tropenylium cation. If an inductively electron-donating group is attached to the cation at the 1st or 3rd carbon position, it has a stabilizing effect, improving the homoaromatic character of the compound.
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The pyrochlore supergroup minerals conform to the general formula, A2−mB2X6−wY1−n, where the m, w, and n variables represent the parameters that indicate incomplete occupancy of the A, Y, and X sites (Atencio et al. 2010). They crystallize isometric system with a space group of Fdm or its subgroups where Betafite has a hexoctahedral class (Hogarth 1977). Site A is generally an 8-coordinated cation with a ~1.0 Å radius, B site is generally a 6-coordinated cation, which contains the elements Ti, Nb, and Ta usually for betafite, (Atencio et al. 2010, site X is generally O but can subjugate to OH and F, and site Y is typically an anion but can also be a vacancy, H2O, or a very large monovalent cation, like Cs, K, and Rb.
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The kryptonium ion, KrH+, is an onium ion, consisting of protonated krypton. Although the existence of the kryptonium cation itself has not been proven, salts of the fluorokryptonium ion, KrF+, are known to exist.
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Magnesium formate is a magnesium salt of formic acid. It is an inorganic compound. It consists of a magnesium cation and formate anion. It can be prepared by reacting magnesium oxide with formic acid.
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The compound features a pyramidal oxonium cation, isoelectronic with triethylamine, and a tetrahedral fluoroborate anion. Reflecting its ionic character, the salt dissolves in polar but inert solvents such as dichloromethane, sulfur dioxide, and nitromethane.
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Many related di-, tri-, and polyphosphates are known including the cyclic triphosphate P3O93−. It binds strongly to metal cations as both a bidentate and tridentate chelating agent. Chelation of a metal cation by triphosphate.
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Californium oxychloride (CfOCl) is a radioactive salt first discovered in measurable quantities in 1960. It is composed of a single californium cation and one oxychloride anion. It was the first californium compound ever isolated.
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When solid nitrogen is irradiated by high speed protons or electrons, several reactive radicals are formed, including atomic nitrogen (N), nitrogen cations (N+), dinitrogen cation (N2+), trinitrogen radicals (N3 and N3+), and azide (N3−).
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12-Crown-4, also called 1,4,7,10-tetraoxacyclododecane and lithium ionophore V, is a crown ether with the formula C8H16O4. It is a cyclic tetramer of ethylene oxide which is specific for the lithium cation.
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T. E. (Thomas Edward) Thorpe. A dictionary of applied chemistry (Volume 4) :PBr5 \+ Br2 → PBr7 The structure consists of a PBr4+ cation paired with a tribromide (Br3–) anion, and the tribromide is non- symmetric.
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The trihydrogen cation is the simplest triatomic molecule, because its two electrons are the only valence electrons in the system. It is also the simplest example of a three-center two-electron bond system.
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Structures of two main types of complexes formed by "methylmercury". X− = anion, L = neutral Lewis base. 3D model of the methylmercury functional group. Methylmercury (sometimes methyl mercury) is an organometallic cation with the formula .
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Aclidinium is a quaternary ammonium cation with an asymmetric carbon atom. It is used as the pure R-enantiomer. The salt, aclidinium bromide, is a crystalline powder that is hardly soluble in water or ethanol.
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Electron-rich arenes are nitrosylated using NOBF4.E. Bosch and J. K. Kochi. "Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation". Journal of Organic Chemistry, 1994, volume 59, pp. 5573–5586.
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The cause for these hereditary conditions is now understood to be various mutations in the erythrocyte membrane protein, band 3. It is this protein which mediates the cation leaks which are characteristic of this disease.
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In Europe, since 2000, the work of the CEDEFOPBjornavold, J. 2001. Making learning visible: identi cation, assessment and recognition of non-formal learning. European Journal of Vocational Training, Vol. 22, pp. 24–32.CEDEFOP. 2009.
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Malvidin-3-O-(6-p-coumaroyl)glucoside is a p-coumaroylated anthocyanin found in grape and wine. There are two forms with the cis and trans isomers of p-coumaric acid. It is a cation.
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Large cation/anion ion exchangers used in demineralization of boiler feedwater. The feedwater must be specially treated to avoid problems in the boiler and downstream systems. Untreated boiler feed water can cause corrosion and fouling.
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Beryllium nitrate, also known as beryllium dinitrate, is an ionic beryllium salt of nitric acid with the chemical formula Be(NO3)2. Each formula unit is composed of one Be2+ cation and two NO3− anions.
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Only the cation MG is deeply colored, whereas the leuco and alcohol derivatives are not. This difference arises because only the cationic form has extended pi-delocalization, which allows the molecule to absorb visible light.
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If the pH is above the pI, the protein will have a negative charge and bind to the matrix in an anion exchange column. The stability of the protein at values above or below the pI, will determine if an anion exchange column or cation exchange column should be used. If it is stable at pH values below the pI, the cation exchange column be used. If it is stable at pH values above the pI then the anion exchange column can be used.
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Moreover, the resulting phenolate anion can stabilize the resulting carbocation through cation-π interactions, which would be particularly strong due to the highly electron-rich nature of the phenolate anion. The allylic cation generated is then attacked by the olefin of a second molecule of FPP, affording a tertiary carbocation. The phenolate anion generated previously then serves as a base to abstract a proton from this adduct to form a cyclopropane product, presqualene pyrophosphate (PSPP). The PSPP created remains associated with SQS for the second reaction.
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It was found that interaction energies of cation–π pairs correlate well with electrostatic potential above the π face of arenes: for eleven Na+-aromatic adducts, the variation in binding energy between the different adducts could be completely rationalized by electrostatic differences. Practically, this allows trends to be predicted qualitatively based on visual representations of electrostatic potential maps for a series of arenes. Electrostatic attraction is not the only component of cation–π bonding. For example, 1,3,5-trifluorobenzene interacts with cations despite having a negligible quadrupole moment.
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The m/z=57 butyl cation is the base peak, and other most abundant peaks in the spectrum are alkyl carbocations at m/z=15, 29, 43 Da. The possible mechanisms for EI ionization spectra of hexane Branched alkanes have somewhat weaker molecular ion peaks in the spectra. They tend to fragment at the branched point. For the 2,3-dimethylbutane, an isopropyl cation peak (m/z=43) is very strong. Branched alkane Cycloalkanes have relatively intense molecular ion peaks (two bonds have to break).
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Laboratory experiments with formamide, a liquid resembling water, have shown how no such dehydration barrier can be involved. The fundamental difficulty to nucleate anhydrous magnesium carbonate remains when using this non-aqueous solution. Not cation dehydration, but rather the spatial configuration of carbonate anions creates the barrier in the low-temperature nucleation of magnesite.Xu, J; Yan, C.; Zhang, F.; Konishi, H., Xu, H. & Teng, H. H. (2013): Testing the cation- hydration effect on the crystallization of Ca – Mg- CO3 systems. Proc. Natl. Acad. Sci.
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Base-cation saturation ratio (BCSR) is a method of interpreting soil test results that is widely used in sustainable agriculture, supported by the National Sustainable Agriculture Information Service (ATTRA)NCat Soil Management and claimed to be successfully in use on over a million acres (4,000 km²) of farmland worldwide. The traditional method, as used by most university laboratories,McLean, E.O. 1977. Contrasting concepts in soil test interpretation: Sufficiency levels of available nutrients versus basic cation saturation ratios. p. 39–54. In T.R. Peck et al.
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MS can be classified based on the type of ion to which they are permeable. Cation Selective MSCs: As the name suggests, they exhibit a selective permeability for positive ions with the most selective channels being those for K+. The most common eukaryotic MSCs are cation selective passing Na+, K+ and Ca2+ but not Mg2+. They have a single channel conductance range (25-35 pS) and they are blocked by trivalent ion Gadolinium. The K+ selective MSCs such as TREK-1 are not blocked by Gd3+.
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Heterolytic bond cleavage is a process where the electron pair that comprised a bond moves to one of the atoms that was formerly joined by a bond. The bond breaks, forming a negatively charged species (an anion) and a positively charged species (a cation). The anion is the species that retains the electrons from the bond while the cation is stripped of the electrons from the bond. The anion usually forms on the most electronegative atom, in this example atom A. :Heterolytic bond cleavage.
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The swapping of this positive cation with another is what makes different types of clays including Kaolinite, montmorillonite, smectite and illite. This happens in marine clays because the ocean's water is high in solution with cations making it very easy to overcome the clays negative net charge and swap the clays cation with a less positive one. These marine clays can be what are known as quick clays, which are notorious for its erosive properties. A great example of these quick clays is in the pacific northwest.
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Biosynthesis of N-methyl-pyrrolinium cation Biosynthesis of cocaine Robinson biosynthesis of tropane Reduction of tropinone The first synthesis and elucidation of the cocaine molecule was by Richard Willstätter in 1898. Willstätter's synthesis derived cocaine from tropinone. Since then, Robert Robinson and Edward Leete have made significant contributions to the mechanism of the synthesis. (-NO3) The additional carbon atoms required for the synthesis of cocaine are derived from acetyl-CoA, by addition of two acetyl-CoA units to the N-methyl-Δ1-pyrrolinium cation.
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Rao is also a member of several national and international societies including the American Association of Science the Federation of American Society of Experimental Biology. As the Principal Investigator of the Rao Lab, Rao leads a research program focused on exploring the role of intracellular cation transport in health and disease. The lab uses yeast as a model organism with which to study the biology of cation transport channels. The specific transporters they focus on are H+-ATPases, Ca2+-ATPases, and Na+/H+ exchangers.
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Ball-and-stick model of the bis(12-crown-4)lithium cation Like other crown ethers, 12-crown-4 complexes with alkali metal cations. The cavity diameter of 1.2-1.5 Å gives it a high selectivity towards the lithium cation (ionic diameter 1.36 Å) Its point group is S4. The dipole moment of 12-crown-4 varies with solvent and temperature. At 25 °C, the dipole moment of 12-crown-4 was determined as 2.33 ± 0.03 D in cyclohexane and 2.46 ± 0.01 D in benzene.
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Polyspecific organic cation transporters in the liver, kidney, intestine, and other organs are critical for elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. This gene is one of three similar cation transporter genes located in a cluster on chromosome 6. The encoded protein contains twelve putative transmembrane domains and is a plasma integral membrane protein. Two transcript variants encoding two different isoforms have been found for this gene, but only the longer variant encodes a functional transporter.
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The adjective "ferrous" is used instead for iron(II) salts, containing the cation Fe2+. The word ferric is derived from the Latin word ferrum for iron. Iron(III) metal centres also occur in coordination complexes, such as in the anion ferrioxalate, , where three bidentate oxalate ions surrounding the metal centre; or, in organometallic compounds, such as the ferrocenium cation , where two cyclopentadienyl anions are bound to the FeIII centre. Iron is almost always encountered in the oxidation states 0 (as in the metal), +2, or +3.
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Example of the use of nucleophilic displacement to make a borenium ion. Displacement of a ligand from a neutral tricoordinate boron halide by a neutral donor such as pyridine results in the generation of a borenium cation. For this reaction to yield the desired borenium cation, the ligand must be a good leaving group and the neutral donor must have enough steric bulk that nucleophilic dissociation is favored over Lewis acid-base adduct formation with the neutral BR3 starting material, as demonstrated by competition experiments.
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H3+, the trihydrogen cation is stable by itself and is symmetric. 4He3, the helium trimer is only weakly bound by van der Waals force and is in an Efimov state. Trisulfur (S3) is analogous to ozone.
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The N terminal domain is well conserved across different species. This may be due to its important function in substrate and cation binding. The residues involved in methionine binding are found in the N-terminal domain.
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Some prototypical examples of species with delocalized bonding. Top row: pyridine, furan, tropylium cation. Second row: allyl radical, acetate ion, acrolein. Atoms involved are in bold red, while electrons involved in delocalized bonding are in blue.
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Organic phosphonium cations are lipophilic and can be useful in phase transfer catalysis, much like quaternary ammonium salts. :Synthesis of phosphonium halides from triphenylphosphine and an alkyl halide The cation tetraphenylphosphonium () is a useful precipitating agent.
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The cation can be considered 9-coordinate or 11-coordinate. The larger sized rare earth elements (lanthanides), which are those with smaller atomic number, also form trifluorides with the LaF3 structure. Some actinides do as well.
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Much of the discussions and studies of both tschermakite and tremolite have been to resolve the varying cation placements and Al substitutions that seem to occur on all T and M sites (Najorka and Gottschalk, 2003).
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The second step leads to an oxocarbocation intermediate, the sialosyl cation. The third step is the formation of Neu5Ac initially as the α-anomer, and then mutarotation and release as the more thermodynamically- stable β-Neu5Ac.
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Polycystin-L has been shown to be a cation (Na+, K+ and Ca2+) channel that is activated by Ca2+, while polycystin-2 has been characterized as a Ca2+-permeable cation- selective channel. Two members of the PCC family (polycystin 1 and 2; PKD1 and 2) are mutated in human autosomal dominant polycystic kidney disease, and polycystin-L, very similar and probably orthologous to PKD2, is deleted in mice with renal and retinal defects. PKD1 and 2 interact to form the non- selective cation channel in vitro, but PKD2 can form channels in the absence of any other associated protein. Polycystin-2 transports a variety of organic cations (dimethylamine, tetraethylammonium, tetrabutylammonium, tetrapropylammonium, tetrapentenyl ammonium). The channel diameter was estimated to be at least 1.1 Å. Both are reported to be integral membrane proteins with 7-11 TMSs (PKD1) and 6 TMSs (PKD2), respectively.
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This cation undergoes a second cyclization to form the thujyl cation intermediate (7) before loss of a proton to form the thujone precursor, (+)-sabinene (8). The conversion of alpha- terpinyl cation to (+)-sabinene From (+)-sabinene (8), the proposed biosynthetic route to generate thujone follows a three-step pathway: (+)-sabinene is first oxidized to an isomer of (+)-sabinol (9-1,2) by a cytochrome P450 enzyme, followed by conversion to (+)-sabinone (10) via a dehydrogenase. Finally, a reductase mediates the conversion to α-thujone (11-1) and β-thujone (11-2). The isomerism of the (+)-sabinol intermediate varies among thujone-producing plants; for instance, in the western redcedar (Thuja plicata), thujone is derived exclusively from the (+)-trans-sabinol intermediate (9-1) whereas in the common garden sage (Salvia officinalis), thujone is formed from the (+)-cis-sabinol intermediate (9-2).
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Royal College of Psychiatrists Annual General Meeting, Edinburgh 2003.Edelstyn N.M., Drakeford J., Oyebode F., Findlay C.D. (2003). An investigation of conscious recollection, false recognition and delusional misidentify cation in patients with schizophrenia. Psychopathology, 36, 312–319.
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The more stable the product cation, the more abundant the corresponding decomposition process. Several theories can be utilized to predict the fragmentation process, such as the electron octet rule, the resonance stabilization and hyperconjugation and so on.
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Hydride abstraction with nitrosonium tetrafluoroborate yields the trisilyl-substituted cyclopropenium cation. :Cyclopropenium synthesis 2 Amino-substituted cyclopropenium salts are particularly stable. Calicene is an unusual derivative featuring cyclopropenium linked to a cyclopentadienide. :Calicene features a cyclopropenium ring.
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In F. Adams (ed.) Soil acidity and liming. Agron. Monogr. 12. 2nd ed. ASA, CSSA, and SSSA, Madison, WI.Liebhardt, W.C. 1981. The basic cation saturation ratio concept and lime and potassium recommendations on Delaware's Coastal Plain soils.
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"Competitive absorption of quaternary ammonium and alkali metal cations into a Nafion cation-exchange membrane." J. Membrane Sci. 215 103-114. The octanol-water partition coefficient of TEA iodide, Po-w was determined experimentally to be (or ).
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The cation [Co(en)3]3+ is octahedral with Co-N distances in the range 1.947–1.981 Å. The N-Co-N angles are 85° within the chelate rings and 90° between nitrogen atoms on adjacent rings.
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Respectively, the average bond lengths are 1.622 Å, 1.622 Å, and 1.624 Å. Yangite is composed of an octahedrally coordinated Mn2+ cation. Within the crystal structure, Pb2+ has a coordination number of five, bonded with O molecules.
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Plant Physiol. 125(4): 1930-40. It was proposed that the methylene of (+)-Costunolide is reduced before the second ring closure. The bicyclic decalin ring system is formed via the eudesmyl cation followed by hydroxylation at C1.
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Tetramethylphosphonium bromide is an organophosphorus compound with the formula (CH3)4PBr. It is a white, water-soluble solid, the salt of the cation tetramethylphosphonium and the bromide anion. It is prepared by treating trimethylphosphine with methyl bromide.
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2nd ed. New York. Oxford University Press. To take into account simultaneously all major cations present in water, a new irrigation water quality parameter was defined: the cation ratio of structural stability (CROSS), a generalization of SAR.
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This method was developed by British physicists Oliver Lodge in 1886 and William Cecil Dampier in 1893. It depends on the movement of the boundary between two adjacent electrolytes under the influence of an electric field. If a colored solution is used and the interface stays reasonably sharp, the speed of the moving boundary can be measured and used to determine the ion transference numbers. The cation of the indicator electrolyte should not move faster than the cation whose transport number is to be determined, and it should have same anion as the principle electrolyte.
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At a fixed magnetic field, a light source illuminates the nanofluid where the colour of the nanofluid changes depending on the cation concentration. This color change occurs within a second after exposure to cations, much faster than other existing cation sensing methods. Such response stimulus nanofluids are also used to detect and image defects in ferromagnetic components. The photonic eye, as it has been called, is based on a magnetically polarizable nano-emulsion that changes colour when it comes into contact with a defective region in a sample.
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Equivalent notations for an iron atom (Fe) that lost two electrons, referred to as ferrous. When writing the chemical formula for an ion, its net charge is written in superscript immediately after the chemical structure for the molecule/atom. The net charge is written with the magnitude before the sign; that is, a doubly charged cation is indicated as 2+ instead of +2. However, the magnitude of the charge is omitted for singly charged molecules/atoms; for example, the sodium cation is indicated as Na+ and not Na1+.
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Cation–π interactions have been observed in the crystals of synthetic molecules as well. For example, Aoki and coworkers compared the solid state structures of Indole-3-acetic acid choline ester and an uncharged analogue. In the charged species, an intramolecular cation–π interaction with the indole is observed, as well as an interaction with the indole moiety of the neighboring molecule in the lattice. In the crystal of the isosteric neutral compound the same folding is not observed and there are no interactions between the tert-butyl group and neighboring indoles.
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SGK1 has also been shown to increase the activity of cell volume-regulated Cl− channel ClC2. The activation of these Cl− channels result in the exit of Cl− and eventually the exit of K+, and the cellular loss of KCl results in a decrease of regulatory cell volume. However, the functional significance of SGK1 in cell volume regulation, along with its stimulation of cation channels, is still not clearly understood. "Moreover, the molecular identity of the cation channels and the mechanisms of their regulation by glucocorticoids and osmotic cell shrinkage have remained elusive".
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Transient receptor potential cation channel subfamily V member 2 is a protein that in humans is encoded by the TRPV2 gene. TRPV2 is a nonspecific cation channel that is a part of the TRP channel family. This channel allows the cell to communicate with its extracellular environment through the transfer of ions, and responds to noxious temperatures greater than 52 °C. It has a structure similar to that of potassium channels, and has similar functions throughout multiple species; recent research has also shown multiple interactions in the human body.
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Axinite- (Mg) is a borosilicate of aluminum, calcium and magnesium of the axinite group, with magnesium as the dominant cation in the place of the structure that can also be occupied by iron and manganese. It was discovered in gem material from Merelani Hills, Lelatema Mts, Manyara region (Tanzania), which is consequently its type locality. It was initially called magnesioaxinite, referring to its membership in the axinite group and the role of magnesium as the dominant cation. The International Mineralogical Association (IMA) later changed its name to axinite- (Mg).
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The hemerythrin/HHE cation- binding domain occurs as a duplicated domain in hemerythrins, myohemerythrins and related proteins. This domain binds iron in hemerythrin, but can bind other metals in related proteins, such as cadmium in the Nereis diversicolor hemerythrin. It is also found in the NorA protein from Cupriavidus necator, this protein is a regulator of response to nitric oxide, which suggests a different set-up for its metal ligands. A protein from Cryptococcus neoformans (Filobasidiella neoformans) that contains haemerythrin/HHE cation-binding domains is also involved in nitric oxide response.
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One spectroscopic technique that was further developed to investigate the 2-norbornyl cation was nuclear magnetic resonance spectroscopy of compounds in highly acidic media. Comparisons of the 2-norbornyl cation to unstable transition states with delocalized electronic states were often made when trying to elucidate whether the norbornyl system was stable or not. These efforts motivated closer investigations of transition states and vastly increased the scientific community’s understanding of their electronic structure. In short, vigorous competition between scientific groups led to an extensive research and a better understanding of the underlying chemical concepts.
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In the BCSR system, soil cations are balanced according to varying ratios often stated as giving 'ideal' or 'balanced' soil. These ratios can be between individual cations, such as the calcium to magnesium ratio, or they may be expressed as a percentage saturation of the cation exchange capacity (CEC) of the soil. Most 'ideal soil' theories stress both approaches. (See also – Cation exchange capacity) Strictly speaking, the 'base' cations are limited to calcium, magnesium, potassium, and sodium, and these are the primary nutrients that BCSR methods are most concerned with balancing.
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Conversely, electron-rich styrenes were found to react via a radical-cation mechanism, utilizing methyl viologen or molecular oxygen as a transient electron sink. While [Ru(bipy)3]2+ proved to be a competent catalyst for intramolecular cyclizations using methyl viologen, it could not be used with molecular oxygen as an electron sink or for intermolecular cyclizations. For intermolecular cyclizations, Yoon et al. discovered that the more strongly oxidizing photocatalyst [Ru(bpm)3]2+ and molecular oxygen provided a catalytic system better suited to access the radical cation necessary for the cycloaddition to occur.
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After formation of a metal enolate, dissociation of halide generates a positively charged oxyallyl intermediate. This electron-deficient 2π component reacts with electron-rich dienes to give cycloheptenones. Cyclic dienes fare better than the corresponding acyclic dienes because in order to react, the diene must be in the s-cis conformation in the presence of the short-lived oxyallyl cation—cyclic dienes are locked in this reactive conformation. (2)File:43Mech1.png Substituents at the 1 and 3 positions are usually required to stabilize the oxyallyl cation and prevent isomerization to cyclopropanones and allene oxides.
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Chromium(III) acetate, commonly known as basic chromium acetate, describes a family of salts where the cation has the formula [Cr3O(O2CCH3)6(OH2)3]+. The trichromium cation is encountered with a variety of anions, such as chloride and nitrate. Data in the table above are for the chloride hexahydrate, [Cr3O(O2CCH3)6(OH2)3]Cl(H2O)6. Salts of basic chromium acetate has long attracted interest because of its distinctive structure, which features octahedral Cr(III) centers, a triply bridging oxo ligand, six acetate ligands, and three aquo ligands.
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482, pp. 193-200. Subunit of crystal structure of H3OBF4 highlighting the hydrogen bonding between the cation and the anion Aqueous solutions of HBF4 are produced by dissolving boric acid in aqueous hydrofluoric acid. Three equivalents of HF react to give the intermediate boron trifluoride and the fourth gives fluoroboric acid: : B(OH)3 \+ 4 HF → H3O+ \+ + 2 H2O Anhydrous solutions can be prepared by treatment of aqueous fluoroboric acid with acetic anhydride.Wudl, F.; Kaplan, M. L., "2,2′-Bi-L,3-Dithiolylidene (Tetrathiafulvalene, TTF) and its Radical Cation Salts" Inorg. Synth.
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The Grotthuss mechanism is now a general name for the proton-hopping mechanism. In liquid water the solvation of the excess proton is idealized by two forms: the H9O4+ (Eigen cation) or H5O2+ (Zundel cation). While the transport mechanism is believed to involve the inter-conversion between these two solvation structures, the details of the hopping and transport mechanism is still debated. Currently there are two plausible mechanisms: # Eigen to Zundel to Eigen (E–Z–E), on the basis of experimental NMR data, # Zundel to Zundel (Z–Z), on the basis of molecular dynamics simulation.
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Mammalian cells are unable to synthesize choline de novo and therefore must rely on exogenous sources from the diet. The uptake of choline is accomplished predominantly by the high-affinity, sodium dependent choline transporter (CHT) and requires ATP as an energy source. On the other hand, choline may enter the cell through the activation of low-affinity, sodium-independent organic cation transport proteins (OCTs) and/or carnitine/organic cation transporters (OCTNs), and do not require ATP. Lastly, choline may enter the cell through intermediate-affinity transporters, which include the choline transporter-like protein 1 (CTL1).
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The van der Waals contact between S-CH3 unit of SAM and the aromatic face of a Trp residue, in favorable alignment for catalysis assisted by cation-π interaction. A great deal of circumstantial evidence places aromatic residues in the active site of a number of proteins that interact with cations but the presence of cation-π interaction in biological system does not rule out the conventional ion-pair interaction. In fact there is a good evidence for the existence of both type of interaction in model system.
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Decamethylsilicocene reacts with inorganic cyanides such as BrCN and through oxidative addition to form a silicon (IV) product with a cyanide ligand along with either a Br or Me3Si ligand. Decamethylsilicocene can be protonated using strong acids such as . Upon protonation, one equivalent of pentamethylcyclopentadiene is eliminated to produce the pentamethylsilicon(II) cation with a . The pentamethylcyclopentadienylsilicon(II) cation reacts with a variety of cyclopentadienyl salts to produce substituted silicocenes. Silicocene derivatives synthesized this way include (Me5C5)((i-Pr)5C5)Si, ((Me5C5)(1,3,4-Me3H2C5)Si and (Me5C5)(H5C5)Si.
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The same effect of crystal growth inhibition is also observed with the cation whose ionic radius is similar to this of . When the cation is incorporated at low concentration in the crystal lattice of calcite in chemical equilibrium with seawater, it also stabilizes the electron-hole centers observable in electron spin resonance (ESR) spectrometry (characteristic ESR line at g = 2.0006 – 2.0007) as evidenced by Barabas et al. (1988, 1992) and others when attempting to unravel the nature of the paramagnetic centers used to date corals and foraminifera in deep sea sediments.
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The sodium salt is the starting point for most BARF derivatives. It is prepared by treating Grignard reagents derived from XC6H3-3,5-(CF3)2 (X = Br, I) with NaBF4. A popular method is summarized in the following equation: :NaBF4 \+ 4 ArFMgBr → 4 MgBrF + NaBArF4 Brookhart's acid is the salt of the BARF anion with the diethyl ether oxonium cation, [(Et2O)2H]BArF4. It can be formed from the sodium salt in diethyl ether in the presence of hydrogen chloride as sodium chloride is insoluble in diethyl ether, facilitating cation exchange.
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Absorption and desorption of the oxygen can be controlled using pressure change, so-called Pressure Swing Adsorption (PSA) or temperature change, so-called Temperature Swing Absorption (TSA). Cation ordered double perovskites BaLnMn2O5+d (Ln: Lanthanides and Y) are known oxygen storage materials working in PSA mode. The materials show practically complete and reversible change between fully reduced BaLnMn2O5 and oxidized BaLnMn2O6, which occurs at moderate temperatures (300–500 °C) during changes of the oxygen partial pressure. The properties of the particular material depends on the substituted Ln3+ cation.
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In general, ion exchangers favor the binding of ions of higher charge and smaller radius. An increase in counter ion (with respect to the functional groups in resins) concentration reduces the retention time. A decrease in pH reduces the retention time in cation exchange while an increase in pH reduces the retention time in anion exchange. By lowering the pH of the solvent in a cation exchange column, for instance, more hydrogen ions are available to compete for positions on the anionic stationary phase, thereby eluting weakly bound cations.
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Ion-exchange resins in the form of thin membranes are also used in chloralkali process, fuel cells, and vanadium redox batteries. Idealised image of water-softening process, involving replacement of calcium ions in water with sodium ions donated by a cation-exchange resin. Large cation/anion ion exchangers used in water purification of boiler feedwater Ion exchange can also be used to remove hardness from water by exchanging calcium and magnesium ions for sodium ions in an ion-exchange column. Liquid-phase (aqueous) ion-exchange desalination has been demonstrated.
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Such epoxidation in post-PKS modications has been seen in epothilone biosynthesis by EpoK. In EpoK, the consensus mechanism of epoxidation by P450 involves the formation of a pi-complex between an oxoferryl pi-cation radical species (FeIV) and the olefin pi bond, followed by electron transfer, formation of the olefin pi-cation radical and finally epoxidation. However, it is also possible that in addition to cytochrome p450, a FAD-dependent monoxygenase is also required to install the epoxide. This codependent process is seen in tirandamycin biosynthesis by TamL.
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Nicotine biosynthesis The biosynthetic pathway of nicotine involves a coupling reaction between the two cyclic structures that comprise nicotine. Metabolic studies show that the pyridine ring of nicotine is derived from niacin (nicotinic acid) while the pyrrolidine is derived from N-methyl-Δ1-pyrrollidium cation. Biosynthesis of the two component structures proceeds via two independent syntheses, the NAD pathway for niacin and the tropane pathway for N-methyl-Δ1-pyrrollidium cation. The NAD pathway in the genus Nicotiana begins with the oxidation of aspartic acid into α-imino succinate by aspartate oxidase (AO).
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Central to the siderophore/siderocalin recognition mechanism are hybrid electrostatic/cation-pi interactions. To evade the host defences, pathogens evolved to produce structurally varied siderophores that would not be recognized by siderocalin, allowing the bacteria to acquire iron.
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In oxidizing conditions it can reversibly react with strong acids to form the ferrocenium cation . The rapid growth of organometallic chemistry is often attributed to the excitement arising from the discovery of ferrocene and its many analogues (metallocenes).
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Chlorhexidine is ineffective against polioviruses and adenoviruses. The effectiveness against herpes viruses has not yet been established unequivocally. Chlorhexidine, like other cation-active compounds, remains on the skin. It is frequently combined with alcohols (ethanol and isopropyl alcohol).
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Other viologens have been commercialized because they can change color reversibly many times through reduction and oxidation. The name viologen alludes to violet, one color it can exhibit, and the radical cation (C5H4NR)2+ is colored intensely blue.
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The cation, which is the active moiety, is called glycopyrronium (INN) or glycopyrrolate (USAN). In June 2018, glycopyrronium was approved by the FDA to treat excessive underarm sweating, becoming the first drug developed specifically to reduce excessive sweating.
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Graphite oxide can be used as a cation exchange membrane for materials such as KCl, HCl, CaCl2, MgCl2, BaCl2 solutions. The membranes were permeable by large alkali ions as they are able to penetrate between graphene oxide layers.
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07370 Wang S, Chennupati R, Kaur H, Iring A, Wettschureck N, Offermanns S. Endothelial cation channel PIEZO1 controls blood pressure by mediating flow-induced ATP release. Journal of clinical investigation. 2016 Dec 1;126(12):4527. doi: 10.1172/JCI87343.
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This compound is a yellow crystalline solid that is used in chemical laboratories as a weak reductant. The iron(II) core is easily oxidized to iron(III), yielding the monovalent cation decamethylferrocenium, and even to higher oxidation states.
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A. Dominic Fortes, Frank Browning, and Ian G. Wood (2012): "Cation substitution in synthetic meridianiite (MgSO4·11H2O) I: X-ray powder diffraction analysis of quenched polycrystalline aggregates". Physics and Chemistry of Minerals, volume 39, issue , pages 419–441.
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The structure of the methoxide ion. Methoxides are organic salts and the simplest alkoxides. Sodium methoxide and potassium methoxide have widespread use, though other metal-cation variants such as lithium methoxide, rubidium methoxide, and caesium methoxide exist as well.
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Therefore, electron-hole recombination is retarded by the physical separation between the dye–cation moiety and the TiO2 surface, as shown in Fig. 5. Finally, this process raises the carrier diffusion length, resulting in the increase of carrier lifetime.
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Polonium is "distinctly metallic" in some ways.Cotton et al. 1999, p. 502 Both of its allotropic forms are metallic conductors. It is soluble in acids, forming the rose-coloured Po2+ cation and displacing hydrogen: Po + 2 H+ → Po2+ \+ H2.
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Nicotinic receptors bind the acetylcholine (ACh) neurotransmitter to produce non-selective cation channel flow that generates excitatory postsynaptic responses. Receptor activity, which can be influenced by nicotine consumption, produces feelings of euphoria, relaxation, and inevitably addiction in high levels.
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The pentazenium cation (also known as pentanitrogen) is a positively charged polynitrogen ion of the chemical formula . Together with dinitrogen, solid nitrogen polymers and the azide anion, it is one of only three polynitrogen species obtained in bulk quantities.
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Carboxylic acids can be regenerated from the carboxylate salts using a process known as "acid springing". This process makes use of a high-molecular-weight tertiary amine (e.g., trioctylamine), which is switched with the cation (e.g., ammonium or calcium).
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Tetrabutylammonium is a quaternary ammonium cation with the formula [N(C4H9)4]+. It is used in the research laboratory to prepare lipophilic salts of inorganic anions. Relative to tetraethylammonium derivatives, tetrabutylammonium salts are more lipophilic but crystallize less readily.
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This gene encodes a transmembrane protein, which is located primarily in the endoplasmic reticulum and ubiquitously expressed with highest levels in brain, pancreas, heart, and insulinoma beta-cell lines. Wolframin appears to function as a cation-selective ion channel.
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When an enol reacts with an electrophile, however, only the initial addition step is the same. Instead of reacting with CI− to give an addition product, the intermediate cation loses the OH− proton to give an α-substituted carbonyl compound.
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This stands in contrast to the 1'-4 linkages that are much more common in isoprene biosynthesis than 4-4' linkages. The reaction mechanism of SQS requires a divalent cation, often Mg2+, to facilitate binding of the pyrophosphate groups on FPP.
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It is the simplest oxocarbon and is isoelectronic with other triply-bonded diatomic species possessing 10 valence electrons, including the cyanide anion, the nitrosonium cation, boron monofluoride and molecular nitrogen. In coordination complexes the carbon monoxide ligand is called carbonyl.
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Transient receptor potential cation channel, subfamily C, member 2, also known as TRPC2, is a protein that in humans is encoded by the TRPC2 pseudogene. This protein is not expressed in humans but is in certain other species such as mouse.
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The nonselective cation channel TrpC4 has been shown to be present in high abundance in the cortico-limbic regions of the brain. In addition, TRPC4 mRNA is present in midbrain dopaminergic neurons in the ventral tegmental area and the substantia nigra.
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The Nicholas reaction is an organic reaction where a dicobalt octacarbonyl- stabilized propargylic cation is reacted with a nucleophile. Oxidative demetallation gives the desired alkylated alkyne. It is named after Kenneth M. Nicholas. The Nicholas reaction Several reviews have been published.
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Pinacyanol is a cyanine dye. It is an organic cation, typically isolated as the chloride or iodide salts. The blue dye is prepared from 2-methylquinoline by quaternization with ethyl chloride or ethyl iodide. Condensation with formaldehyde results in coupling.
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If an organic solution of permanganate is desired, "purple benzene" may be prepared, either by treating a two phase mixture of aqueous potassium permanganate and benzene with a quaternary ammonium salt, or by sequestering the potassium cation with a crown ether.
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Hercynite is a spinel of regular symmetry and normal cation distribution, but some disorder occurs in its structure. It consists of ferrous (Fe2+) ions and aluminium ions (Al3+), however some ferric ions (Fe3+) may be located in the structure of hercynite.
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Espeletia killipii Cuatrec. Espeletia picnophyla Cuatrec. Espeletia schultzii (Benth.) W.M.Curtis and Espeletia curialensis Cuatrec. The Sphagnum moss covers wide areas of Sumapaz, which increases the soil's capacity to hold water and nutrients by increasing capillary forces and cation exchange capacity.
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The structure of a cobalt(IV) coordination complex with the norbornyl anion Reaction of the anhydrous compound with sodium cyclopentadienide gives cobaltocene . This 19-electron species is a good reducing agent, being readily oxidised to the yellow 18-electron cobaltacenium cation .
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ZS-9 is an inorganic cation exchanger crystalline with a high capacity to entrap monovalent cations, specifically potassium and ammonium ions, in the GI tract. ZS-9 is not systemically absorbed; accordingly, the risk of systemic toxicity may be minimized.
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20-HETE activates the mouse and human transient receptor potential cation channel subfamily V member 1 (TRPV1, also known as the capsaicin receptor and the vanilloid receptor 1), and through this receptor, cultured dorsal root ganglion cells taken from mice.
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Solute carrier family 22 (organic cation transporter), member 21 is a protein that in the house mouse is encoded by the Slc22a21 gene. The gene is also known as Octn3 and Slc22a9. Slc22a21 belongs to a protein family of solute carriers.
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Lithium triflate (lithium triflouromethanesulfonate or LiOTf) is a salt with the chemical formula LiCF3SO3. It is composed of the lithium cation (Li+) and triflate anion (CF3SO3−; TfO−). It is very hygroscopic. The salt is used in lithium-ion battery production.
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East Bear Brook has been used as an untreated reference. Related research topics at BBWM include climate change, carbon sequestration, base cation depletion, and watershed biogeochemistry. There are two USGS stream gauges on the East and West Branches of Bear Brook.
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The cation can be quantitatively precipitated from its yellow-gray chromate and hexachloroplatinate salts. When treated with concentrated hydrochloric acid, hexol converts to cis- diaquotetramminecobalt(III) sulfate. In boiling dilute sulfuric acid, hexol degrades with evolution of oxygen and nitrogen.
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Hydrazinium azide or hydrazine azide is a chemical compound with formula or . It is a salt of the hydrazinium cation and the azide anion . It can be seen as a derivative of hydrazine and hydrazoic acid . It is an unstable solid.
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No reaction occurs with trimethylarsine or trimethylstibine. Methyl lithium reacting with the Trimethylborane produces a tetramethylborate salt: LiB(CH3)4.Georg Wittig in 1958 The tetramethylborate ion has a negative charge and is isoelectronic with neopentane, tetramethylsilane, and the tetramethylammonium cation.
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Calcium is a divalent cation, allowing it to form bonds with several caseinate anions. This leads to the formation of several covalent bonds between caseinate anions, which can ultimately cause the cross-linked caseinate to form pockets of hydrophobic regions.
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Masters dissertation, University of the Western Cape; Whitley, D.S. & Annegarn, H.J. 1994. Cation-ratio dating of rock engravings from Klipfontein, Northern Cape. In Dowson, T.A. & Lewis-Williams, J.D. (eds) Contested images: diversity in southern African rock art research:189-197.
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Specifically, the mechanism involves hybrid electrostatic and cation-pi interactions in the positively charged protein calyx. The siderophore is positioned in the centre of the siderocalin calyx, and is associated with multiple direct polar interactions. Structural analysis of the siderocalin/siderophore interaction has shown that the siderophore is accompanied by a poor and diffuse quality of electron density, with the majority of the ligand exposed to the solvent when the siderophore is fit in the calyx. Siderocalin typically does not bind hydroxamate-based siderophores because these substrates do not have the necessary aromatic electronic structure for cation-pi interactions.
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Donnan dialysis is a separation process which is used to exchange ions between two aqueous solutions which are separated by a CEM or an AEM membrane. In case of having a cation exchange membrane and two solutions with different acidity, protons (H+) go through the membrane to the less acid side. It induces an electrical power that will instigate a flux of the cations present in the less acid side to the more acid side. The process will finish when the variation of concentration of H+ is the same order of magnitude as the difference of concentration of the separated cation.
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400px Electrodialysis (ED) is used to transport salt ions from one solution through ion-exchange membranes to another solution under the influence of an applied electric potential difference. This is done in a configuration called an electrodialysis cell. The cell consists of a feed (dilute) compartment and a concentrate (brine) compartment formed by an anion exchange membrane and a cation exchange membrane placed between two electrodes. In almost all practical electrodialysis processes, multiple electrodialysis cells are arranged into a configuration called an electrodialysis stack, with alternating anion and cation exchange membranes forming the multiple electrodialysis cells.
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Given the toxicity of lead, there is ongoing research into the discovery of lead-free perovskites for optoelectronics. Several lead-free perovskites have been prepared colloidally: Cs3Bi2I9, Cs2PdX6, CsSnX3. CsSnX3 NCs, although the closest lead-free analogue to the highly luminescent CsPbX3 NCs, do not exhibit high quantum yields (<1% PLQY) CsSnX3 NCs are also sensitive towards O2 which causes oxidation of Sn(II) to Sn(IV) and renders the NCs non-luminescent. Another approach to this problem relies on the replacement of the Pb(II) cation with the combination of a monovalent and a trivalent cation i.e.
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Furthermore, this directly alters the energy of emitted light according to the Stokes shift of the material. This quick, post- synthetic anion-tunability is in contrast to other quantum dot systems where emission wavelength is primarily tuned through particle size by altering the degree of quantum confinement. Aside from tuning the absorption edge and emission wavelength by anion substitution, it was also observed that the A-site cation also affects both properties. This occurs as a result of the distortion of the perovskite structure and the tilting of octahedra due to the size of the A-cation.
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The ketal protecting groups of _9_ are hydrolyzed to produce the diketone _10_ , which in turn is cyclized to form the cyclopentenone _11_. The ketone of _11_ is reacted with methyl lithium to yield the tertiary alcohol _12_ , which in turn is treated with acid to produce the tertiary cation _13_. The key step of the synthesis is the π-cation cyclization of _13_ in which the B-, C-, and D-rings of the steroid are simultaneously formed to produce _14_. This step resembles the cationic cyclization reaction used in the biosynthesis of steroids and hence is referred to as biomimetic.
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In most cases, the acid form of the copolymer is synthesized (i.e. 100% of the carboxylic acid groups are neutralized by hydrogen cations) and the ionomer is formed through subsequent neutralization by the appropriate metal cation. The identity of the neutralizing metal cation has an effect on the physical properties of the ionomer; the most commonly used metal cations (at least in academic research) are zinc, sodium, and magnesium. Neutralization or ionomerization, can also be accomplished in two ways: the acid copolymer can be melt-mixed with a basic metal or neutralization can be achieved through solution processes.
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After olfactory neurons depolarize in response to an odorant, the G-protein mediated second messenger response activates adenylyl cyclase, increasing cyclic AMP (cAMP) concentration inside a cell, which then opens a cyclic nucleotide gated cation channel. The influx of Ca2+ ions through this channel triggers olfactory adaptation immediately because Ca2+/calmodulin- dependent protein kinase II or CaMK activation directly represses the opening of cation channels, inactivates adenylyl cyclase, and activates the phosphodiesterase that cleaves cAMP. These series of actions by CaMK, desensitizes olfactory receptors to prolonged odorant exposure. An ORN or an Olfactory Receptor Neuron alert goes off to detect the smell.
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Cyclophane host–guest complex Some of the first studies on the cation–π interaction involved looking at the interactions of charged, nitrogenous molecules in cyclophane host–guest chemistry. It was found that even when anionic solubilizing groups were appended to aromatic host capsules, cationic guests preferred to associate with the π-system in many cases. The type of host shown to the right was also able to catalyze N-alkylation reactions to form cationic products. More recently, cation–π centered substrate binding and catalysis has been implicated in supramolecular metal-ligand cluster catalyst systems developed by Raymond and Bergman.
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An ionic bond is formed when a metal loses one or more of its electrons, becoming a positively charged cation, and the electrons are then gained by the non-metal atom, becoming a negatively charged anion. The two oppositely charged ions attract one another, and the ionic bond is the electrostatic force of attraction between them. For example, sodium (Na), a metal, loses one electron to become an Na+ cation while chlorine (Cl), a non-metal, gains this electron to become Cl−. The ions are held together due to electrostatic attraction, and that compound sodium chloride (NaCl), or common table salt, is formed.
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PubMed ; PubMed Central PMCID: PMC1225660 Karlish SJ, Stein WD. Cation activation of the pig kidney sodium pump: transmembrane allosteric effects of sodium. J Physiol. 1985 Feb;359:119–49. PubMed ; PubMed Central PMCID: PMC1193368. An important finding was that trapping or “occlusion” of the K and Na ions in the protein has the functional role of minimizing wasteful cation leakages through the system, thus ensuring optimal efficiency of energy coupling between ATP (Adenosine Triphosphate) hydrolysis and active Na and K ion movements, 3 Na ions out of and 2 K ions into the cell per cycle, respectively.
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Evidence of the non-classical nature of the 2-norbornyl cation grew over the course of several decades, mainly through spectroscopic data gathered using methods such as nuclear magnetic resonance (NMR). Crystallographic confirmation of its non-classical nature did not come until 2013. Although most chemists now agree that 2-norbornyl cation itself is non-classical, it is also widely recognized that the energetic landscape for carbocations tends to be "flat", with many potential structures differing only minutely in energy. Certainly, not all bicyclic carbocations are non-classical; the energy difference between classical and non-classical structures is often delicately balanced.
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Each partial bond is represented as a full bond in one of the three resonance structures or as a dashed partial bond if the cation is depicted through a single structure. Figure 3: Bonding molecular orbital in the non- classical depiction of the 2-norbornyl cation There has been some debate over how much the pi-bonded resonance structure actually contributes to the delocalized electronic structure. Through H and C NMR spectroscopy, it has been confirmed that little positive charge lies on methylene carbon 6. This is unsurprising as primary carbocations are much less stable than secondary carbocations.
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Other simple cations such as protonated acetylene (ethynium, ), protonated ethylene (ethenium, ), and protonated ethane (ethanium, ) have been shown to be best described as non- classical through infrared spectroscopy. The most frequently proposed molecular orbital depiction of the 2-norbornyl cation is shown in Figure 3. Two p-type orbitals, one on each of carbons 1 and 2, interact with a sp- hybridized orbital on carbon 6 to form the hypovalent bond. Extended Hückel Theory calculations for the 2-norbornyl cation suggest that the orbital on carbon 6 could instead be sp-hybridized, though this only affects the geometry of the geminal hydrogens.
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Indeed, many papers reporting stable non-classical ions were later retracted for being unrealistic or incorrect. After publishing this controversial view in 1962, Brown began a quest to find experimental evidence incompatible with the delocalized picture of bonding in the 2-norbornyl cation. Brown also worked to prove the instability of a delocalized electronic structure for the 2-norbornyl cation. If the non-classical ion could be proven to be higher in energy than the corresponding classical ion pair, the non-classical ion would only be seen as a transition state between the two asymmetric cations.
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Raman spectra of the 2-norbornyl cation show a more symmetric species than would be expected for a pair of rapidly equilibrating classical ions. Since the proposed reaction rates for the classical ion rearrangements are slower than the Raman timescale, one would expect the Raman spectra to indicate a less symmetric species if the classical picture were correct. Some studies of the C NMR in particular favored interpretation via the protonated nortricyclene structure. In addition, Raman spectra of the 2-norbornyl cation in some acidic solvents show an absorption band at 3110 cm indicative of an electron-depleted cyclopropane ring.
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Pain sensation can be initiated by nociceptor cells that are sensory neurons with cell bodies located in the dorsal root ganglia. Some nociceptors respond to low pH and the pH-sensitive amiloride-sensitive cation channel 3 has been described as a modulator of acid-induced pain sensation. However, results with amiloride-sensitive cation channel 3 gene knockout mice suggest that those channels do not fully account for acid-induced pain sensation. Proton-sensing G protein-coupled receptors have been shown to be expressed in small-diameter neurons responsible for nociception where they may play a role in acid-induced pain sensation.
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Adapted from Other leaving groups, such as hypervalent iodine moities (which are 1 million fold better leaving groups than the classic triflates), have been utilized to such end as well. Hinkle and coworkers synthesized a number of alkenyl(aryl)iodonium triflates from hypervalent phenyliodo precursors. In the scheme shown, the E- and Z-vinyl triflates form after heterolytic carbon-iodine bond cleavage and subsequent trapping of the cation by triflate. The presence of both E- and Z- vinyl triflate products offers support for the formation of a primary vinyl cation reactive intermediate; through SN2 chemistry, both only one isomer would form.
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However, in vinyl cations, this rearrangement is uncommon even though the rearrangement product in thermodynamically stable. Much like the aryl- substituted vinyl cations, the interacting orbitals during the conversion of a linear vinyl cation to a non-linear allyl cation are orthogonal and passes through a non-planar transition state, which makes the rearrangement difficult. This is evident in the higher activation energies of 1,2-hydride shifts in vinyl cations compared to alkyl cations. Examples of reactions in which this is observed would be the protonation of di-alkyl substituted alkynes and in the solvolysis of ispropylvinyl trifluromethanesulfonate in trifluoroethanol.
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Principle of CEC measurement in soilCation- exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained. Barium (Ba2+) and ammonium (NH4+) are frequently used as exchanger cations, although many other methods are available. CEC measurements depend on pH, and therefore are often made with a buffer solution at a particular pH value. If this pH differs from the natural pH of the soil, the measurement will not reflect the true CEC under normal conditions.
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Paul Attfield has made distinctive contributions to the experimental understanding of structure in the solid- state, in particular pioneering the use of resonant X-ray scattering to study cation and valence ordering effects and characterising charge-order in strongly correlated systems such as magnetite. He introduced the cation-size variance as a concept to rationalise and predict disorder effects, with a substantial impact on the study and preparation of technologically important materials. He has synthesised and characterised new materials with novel electronic properties, including high-Tc superconductivity, colossal magnetoresistance, and negative thermal expansion, including new developments in chemical synthesis.
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While supposedly less favored energetically, the steric properties of some molecules promote the formation of open C-H-C bridges, as shown below in Scheme 2. In 1978 T.S. Sorenson obtained NMR evidence for hydrido-bridged carbocations with 3-center 2-electron bonds through using the 1,6-dimethyl-1-cyclodecyl cation. The steric restriction of the ten-membered ring allowed the formation of a bridging hydrogen species. Expanding upon this approach, in 1992 McMurry developed the in-bicyclo[4,4,4]-1-tetradecyl cation, where the additional ring vastly improved the stability of the molecule by maintain a more rigid structure around the hydrogen bridge.
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Dioxygenyl hexafluoroplatinate(V) has a rhombohedral crystal structure at low temperatures, and a cubic structure at high temperatures, isomorphous to potassium hexafluoroplatinate(V), . Its ionic lattice is indicated by its insolubility in carbon tetrafluoride. In its cubic form, the octahedra are slightly compressed along the three-fold rotational axis, along which the long axis of the cations also lies. Each cation is surrounded by 12 fluorine atoms, 6 of which surround it in a puckered six-membered ring, and of the remaining 3 each belong to the two octahedra lying along the long axis of the cation.
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Randomly oriented XRD samples are not as useful for clay minerals because clays typically have similar X and Y dimensions. The Z dimension differs from clay to clay and is most diagnostic because the Z dimension represents the height of the tetrahedral-octahedral (T-O) or tetrahedral- octahedral-tetrahedral (T-O-T) layer. The Z dimension can increase or decrease because of substitution of the central cation in both the tetrahedral and octahedral layers. The presence and size of a charge balancing cation in the interlayer of T-O-T clays will also affect the Z dimension.
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The following oxidation–reduction tree for a simple ionic compound, AX, where A is a cation and X is an anion, summarizes the various ways in which intrinsic defects can form. Depending on the cation-to-anion ratio, the species can either be reduced and therefore classified as n-type, or if the converse is true, the ionic species is classified as p-type. Below, the tree is shown for a further explanation of the pathways and results of each breakdown of the substance. Tree diagram representation of the oxidation and reduction states resulting from intrinsic defects in ionic compounds.
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The authors noted that this sodium salt could be handled in air as well as water without major decomposition; this emphasises the significance of the accompanying counter cation in stabilisation of PCO. _Scheme 3:_ Grutzmacher's synthesis of the sodium salt of PCO from 2011. Direct carbonylation was a method also employed by Goicoechea in 2013 in order to synthesis a phosphaethynolate anion stabilised by a potassium cation sequestered in 18-crown-6 (see Scheme 4). This method required the carbonylation of solutions of K3P7 at 150 °C and produced by-products that were readily separated during aqueous work ups.
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It is widely believed that most terpenes are derived from the biochemically active isoprene units, isopentenyl pyrophosphate (IPP) and γ,γ-dimethylallyl pyrophosphate (DMAPP). There are two possible pathways that produce these two important precursors, the mevalonate pathway (MVA) which occurs in the cytosol and the methylerythritol phosphate pathway (MEP) or non-mevalonate pathway, which occurs in plastids. IPP and DMAPP are then connected in a head-to-tail fashion to form the backbone of terpenes. Ionization of DMAPP to form the allylic cation which the double bond of IPP regioselectively adds to form the tertiary cation.
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Most soils contain organic colloidal particles called humus as well as the inorganic colloidal particles of clays. The very high specific surface area of colloids and their net electrical charges give soil its ability to hold and release ions. Negatively charged sites on colloids attract and release cations in what is referred to as cation exchange. Cation-exchange capacity (CEC) is the amount of exchangeable cations per unit weight of dry soil and is expressed in terms of milliequivalents of positively charged ions per 100 grams of soil (or centimoles of positive charge per kilogram of soil; cmolc/kg).
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While they are reactive intermediates, hydrogen bridged cations can be stabilized sterically. Hydrogen bridged cations are generally formed by producing a carbocation through the addition of a proton to an alcohol or alkene. Instead of continuing the reaction through the nucleophile addition of the conjugate base to the carbocation, a neighboring C-H bond can interact with the carbocation to form the hydrogen bridge. In Sorensen's 1978 synthesis and observation of the 1,6-dimethyl-1-cyclododecyl anion, the hydroxyl group of 1,6-dimethyl-1-cyclodecanol was removed using fluorosulfonic acid. This allowed the formation of the 1,6 hydrogen bridge. With McMurry's in- bicyclo[4.4.4]-tetradecyl cation, the alkene across from the methyne hydrogen was protonated by trifluoroacetic acid (TFA) to allow a bridge to the tertiary carbocation bridgehead. Final steps in the synthesis of (a) 1,6-dimethyl-1-cyclodecyl cation, first characterized by T.S. Sorensen in 1978 and (b) the in-bicyclo[4.4.4]-1-tetradecyl cation which J. E. McMurry synthesized in 1992.
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The intense green color of the cation results from a strong absorption band at 621 nm (extinction coefficient of ). Malachite green is prepared by the condensation of benzaldehyde and dimethylaniline to give leuco malachite green (LMG): :C6H5CHO + 2 C6H5N(CH3)2 → C6H5CH(C6H4N(CH3)2)2 \+ H2O Second, this colorless leuco compound, a relative of triphenylmethane, is oxidized to the cation that is MG: :C6H5CH(C6H4N(CH3)2)2 \+ HCl + O2 → [C6H5C(C6H4N(CH3)2)2]Cl + H2O A typical oxidizing agent is manganese dioxide. On the left is leuco-malachite Green (LMG) and on the right are the two equivalent resonance structures of the MG cation. The alcohol derivative of MG is derived from LMG by replacement of the unique C–H by C–OH. Hydrolysis of MG gives an alcohol:Adina Raducan, Alexandra Olteanu, Mihaela Puiu, Dumitru Oancea "Influence of surfactants on the fading of malachite green" Central European Journal of Chemistry, 2008, Volume 6, pp.
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Still, in most cases, catalysts are necessary for substitution reactions to occur. The cyclopentadienyl anion () with six π electrons is planar and readily generated from the unusually acidic cyclopentadiene (pKa 16), while the corresponding cation with four π electrons is destabilized, being harder to generate than a typical acyclic pentadienyl cations and is thought to be antiaromatic. Similarly, the tropylium cation (), also with six π electrons, is so stable compared to a typical carbocation that its salts can be crystallized from ethanol. On the other hand, in contrast to cyclopentadiene, cycloheptatriene is not particularly acidic (pKa 37) and the anion is considered nonaromatic. The cyclopropenyl cation () and the triboracyclopropenyl dianion () are considered examples of a two π electron system, which are stabilized relative to the open system, despite the angle strain imposed by the 60° bond angles. Planar ring molecules with 4n π electrons do not obey Hückel's rule, and theory predicts that they are less stable and have triplet ground states with two unpaired electrons.
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Yttrium(III) nitrate mainly uses as a source of Y3+ cation. It is a precursor of some yttrium-containing materials, such as Y4Al2O9, YBa2Cu3O6.5+x and yttrium-based metal-organic frameworks. It can also be used as a catalyst in organic synthesis.
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Iron(II) oxide (ferrous oxide), FeO. Iron(II) chloride tetrahydrate, . In chemistry, iron(II) refers to the element iron in its +2 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe2+.
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Aluminium nitrate may also be prepared a metathesis reaction between aluminium sulfate and a nitrate salt with a suitable cation such as barium, strontium, calcium, silver, or lead. e.g. Al2(SO4)3 \+ 3 Ba(NO3)2 → 2 Al(NO3)3 \+ 3 BaSO4.
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Cations are smaller than the corresponding parent atom or molecule due to the smaller size of the electron cloud. One particular cation (that of hydrogen) contains no electrons, and thus consists of a single proton - much smaller than the parent hydrogen atom.
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The Pseudomonas syringae HrpZ Cation Channel (HrpZ) Family (TC# 1.C.56) is a member of the RTX-toxin superfamily. The Harpin-PSS (HrpZ; TC# 1.C.56.1.1) protein is secreted by Pseudomonas syringae via the Hrp secretion system (IIISP; TC# 3.
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The precise function of the YecM domain remains to be elucidated. However, YecM structural homologues reveal that all the proteins bind a divalent metal cation. This comparison suggests that YecM may be a metal-binding protein and therefore may function as an enzyme.
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In solid [NH4][HF2], each ammonium cation is surrounded by four fluoride centers in a tetrahedron, with hydrogen- fluorine hydrogen bonds present between the hydrogen atoms of the ammonium ion and the fluorine atoms. Solutions contain tetrahedral [NH4]+ cations and linear [HF2]− anions.
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Recent work has demonstrated a close link between seizure activity and high extracellular glutamate in tumor-related epilepsy. Glutamate activation of ionotropic receptors leads to a rapid excitatory signal based on cation influx that can cause release of calcium from intracellular stores.
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TRPP2 is a member of the polycystin protein family. TRPP2 contains multiple transmembrane domains, and cytoplasmic N- and C-termini. TRPP2 may be an integral membrane protein involved in cell- cell/matrix interactions. TRPP2 functions as a calcium-regulated nonselective cation channel.
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However, because it only detects LPS endotoxins, some pyrogenic materials can be missed. Also, certain conditions (sub-optimal pH conditions or unsuitable cation concentration) can lead to false negatives. Glucans from carbohydrate chromatography matrices can also lead to false positives.[Sandle, T. (2013).
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It has been observed spectroscopically but has not been isolated as a pure substance. The salts and esters of thiocyanic acid are known as thiocyanates. The salts are composed of the thiocyanate ion (−SCN) and a suitable metal cation (e.g., potassium thiocyanate, KSCN).
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There is debate on whether a vinyl cation intermediate forms with the addition of a halide (H-X) compound to a terminal alkyne for hydrohalogenation reactions. Alternatively, some believe that the addition of H and Br in this case is actually concerted.
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The diastereoselectivity of nucleophilic attack on this intermediate is much lower than the stereoselectivity of attack on cyclic cation 1. Because of this low stereoselectivity, deoxyribonucleosides are usually synthesized using methods other than the SHJ reaction.Prystas, M.; Šorm, F. ChemPlusChem 1964, 29, 121.
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Choline chloride is an organic compound with the formula (CH3)3NCH2CH2OH]Cl. It is bifunctional, containing both quaternary ammonium salt and an alcohol. The cation is choline, which occurs naturally. It is a white, water-soluble salt used mainly in animal feed.
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This is actually due to a change in C-H-C bond angle, where change in bond angle affects the bonding nature of the 3 center-2 electron bond. The classical and non- classical bonding of the in-bicyclo[4.4.4]-1-tetradecyl cation.
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Ionic liquid is a group of salt modification by anion and cation discret. It has flexibility to exhibit antibiofim activity and has antimicrobial activity, it has many antibiofilm activities and prevents the biofilm formation for many gram-positive and gram- negative bacteria.
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Coenzyme M is a coenzyme required for methyl-transfer reactions in the metabolism of methanogens. The coenzyme is an anion with the formula . It is named 2-mercaptoethanesulfonate and abbreviated HS–CoM. The cation is unimportant, but the sodium salt is most available.
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In hexamminecobalt(III) chloride ([Co(NH3)6]Cl3), the cobalt cation plus the 6 ammonia ligands comprise the first coordination sphere. The coordination sphere of this ion thus consists of a central MN6 core "decorated" by 18 N−H bonds that radiate outwards.
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This transfer of electrons is termed electrovalence in contrast to covalence. In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complicated nature, e.g. molecular ions like NH4+ or SO42−.
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After production, the fermium must be > separated from other actinides and from lanthanide fission products. This is > usually achieved by ion-exchange chromatography, with the standard process > using a cation exchanger such as Dowex 50 or TEVA eluted with a solution of > ammonium α-hydroxyisobutyrate.
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Each molecule of actin is bound to a molecule of adenosine triphosphate (ATP) or adenosine diphosphate (ADP) that is associated with a Mg2+ cation. The most commonly found forms of actin, compared to all the possible combinations, are ATP-G-Actin and ADP-F-actin.
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The adamantane cation can be produced by treating 1-fluoro-adamantane with SbF5. Its stability is relatively high. The dication of 1,3-didehydroadamantane was obtained in solutions of superacids. It also has elevated stability due to the phenomenon called "three-dimensional aromaticity" or homoaromaticity.
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Benzenediazonium cation Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halogen.
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Dequalinium is a quaternary ammonium cation and bolaamphiphile commonly available as the dichloride salt. The bromide, iodide, acetate, and undecenoate salts are known as well. Dequalinium chloride is the active ingredient of several medications: Dequadin an antiseptic and disinfectant. It is a topical bacteriostat.
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J. Chem. 1978, 52, 547. Intramolecular delivery of fluoride has been invoked to explain the formation of difluoromethyl cations. Attack of a molecule of acyl fluoride on a difluoromethyl cation, followed by neutralization with in situ generated bifluoride, leads to α-tetrafluorinated ether products.
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Harmata, M.; Elahmad, S.; Barnes, C. L. Tetrahedron Lett. 1995, 36, 1397. (1)File:43Gen.png Recent developments have focused on expanding the scope of enantioselective (4+3) cycloadditions and the range of conditions available for generating the key oxyallyl cation (propenylium-2-olate) intermediate.
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The fluoronium ion is an inorganic cation with the chemical formula . It is one of the cations found in fluoroantimonic acid. The structure of the salt with the anion, has been determined. The fluoronium ion is isoelectronic with the water molecule and the azanide ion.
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This indicates the proximity of boron to the metal-nonmetal borderline.Fehlner 1990, p. 202 Most of the chemistry of boron is nonmetallic in nature. Unlike its heavier congeners, it is not known to form a simple B3+ or hydrated [B(H2O)4]3+ cation.
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Tetrapropylammonium perruthenate (TPAP or TPAPR) is the chemical compound described by the formula N(C3H7)4RuO4. Sometimes known as the Ley–Griffith reagent, this ruthenium compound is used as a reagent in organic synthesis. This salt consists of the tetrapropylammonium cation and the perruthenate anion, .
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New J. Chem. 2014, 38, 845-851. orally as this is easier to pronounce and remember. It is pertinent to mention that Rathore and Kochi Rathore, R.; Kochi, J. K. Radical-Cation Catalysis in the Synthesis of Diphenylmethanes via the Dealkylative Coupling of Benzylic Ethers.
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Archie's law postulates that the rock matrix is non-conductive. For sandstone with clay minerals, this assumption is no longer true in general, due to the clay's structure and cation exchange capacity. The Waxman–Smits equation is one model that tries to correct for this.
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The S. aureus delta toxin molecule has been speculated to oligomerize and form cation-selective ion channels in the membrane for use other than cell lysis by the toxin. The channel is proposed to be formed by six delta toxin molecules in a hexagonal arrangement.
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If the substrate is an alcohol, it is protonated and subsequently eliminated, generating a carbocation that is converted to an acylium cation by carbon monoxide and then hydrolysed. Tertiary carbocation formation is typically thermodynamically favored when considering hydride or alkyl shifts in the carbocation.
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Another difference is that the iron cation is not diamagnetic low spin Fe(II) as in pyrite. In the crystal structure, each metal ion is tetrahedrally coordinated to 4 sulfur anions. Each sulfur anion is bonded to two copper atoms and two iron atoms.
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In late 2016 imidazolium fluoride was synthesized that is the closest approximation of a thermodynamically stable and structurally characterized example of a "naked" fluoride source in an aprotic solvent (acetonitrile). The sterically demanding imidazolium cation stabilizes the discrete anions and protects them from polymerization.
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If the taste is salty Na+, sodium, molecules pass through the Na+ channels. Depolarization takes place II. Part II is the transduction pathway of the relay molecules.2. Cation, such as K+, channels are opened. III. Part III is the response of the cell. 3.
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The homoaromatic 1-hydroxyhomotropylium cation. Journal of the American Chemical Society (1967), 89(8), 1965-6.Brookhart, Maurice; Lustgarten, Ronald K.; Winstein, Saul. Bridge flipping and rearrangement of norbornadienyl and 7-methylnorbornadienyl cations. Journal of the American Chemical Society (1967), 89(24), 6352-4.
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Cadmium oxide is an inorganic compound with the formula CdO. It is one of the main precursors to other cadmium compounds. It crystallizes in a cubic rocksalt lattice like sodium chloride, with octahedral cation and anion centers.Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. .
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In organic synthesis, EtBr is the synthetic equivalent of the ethyl carbocation (Et+) synthon. In reality, such a cation is not actually formed. For example, carboxylates salts are converted to ethyl esters, carbanions to ethylated derivatives, thiourea into ethylisothiouronium salts, and amines into ethylamines.
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500px In the vast majority of cases, reactions that involve leaving group activation generate a cation in a separate step, before either nucleophilic attack or elimination. For example, SN1 and E1 reactions may involve an activation step, whereas SN2 and E2 reactions generally do not.
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The first NMR spectrum of a stable carbocation in solution was published by Doering et al. in 1958. It was the heptamethylbenzenium ion, made by treating hexamethylbenzene with methyl chloride and aluminium chloride. The stable 7-norbornadienyl cation was prepared by Story et al.
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Starting in the 1970s, melonates have attracted new interest, motivated by research in cubic carbon nitride c-. Salts of many cations have been synthesized and studied, including mixed-cation salts and calcium hydrogenmelonate . The structure of potassium melonate pentahydrate was elucidated only in 2005.
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The resulting macrocyclic diamine tetraether reacts with a second equivalent of [CH2OCH2COCl]2 to produce the macrobicyclic diamide. This di(tertiary)amide is reduced to the diamine by diborane. [2.2.2]Cryptand binds K+ as an octadentate N2O6 ligand. The resulting cation [K(cryptand)]+ is lipophilic.
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The lightest heteronuclear ion is the helium hydride ion (HeH+). This is in contrast to a homonuclear ion, which contains all the same kind of atom, such as the dihydrogen cation, or atomic ions that only contain one atom such as the hydrogen anion (H−).
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The hydrogen atoms in the ammonium ion can be substituted with an alkyl group or some other organic group to form a substituted ammonium ion (IUPAC nomenclature: aminium ion). Depending on the number of organic groups, the ammonium cation is called a primary, secondary, tertiary, or quaternary. With the exception of the quaternary ammonium cations, the organic ammonium cations are weak acids. An example of a reaction forming an ammonium ion is that between dimethylamine, (CH3)2NH, and an acid to give the dimethylammonium cation, (CH3)2NH: :400px Quaternary ammonium cations have four organic groups attached to the nitrogen atom, they lack a hydrogen atom bonded to the nitrogen atom.
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Magnesium is the eighth-most-abundant element in the Earth's crust by mass and tied in seventh place with iron in molarity. It is found in large deposits of magnesite, dolomite, and other minerals, and in mineral waters, where magnesium ion is soluble. Although magnesium is found in more than 60 minerals, only dolomite, magnesite, brucite, carnallite, talc, and olivine are of commercial importance. The cation is the second-most-abundant cation in seawater (about ⅛ the mass of sodium ions in a given sample), which makes seawater and sea salt attractive commercial sources for Mg. To extract the magnesium, calcium hydroxide is added to seawater to form magnesium hydroxide precipitate.
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Usually ionomer synthesis consists of two steps – the introduction of acid groups to the polymer backbone and the neutralization of some of the acid groups by a metal cation. In very rare cases, the groups introduced are already neutralized by a metal cation. The first step (introduction of acid groups) can be done in two ways; a neutral non-ionic monomer can be copolymerized with a monomer that contains pendant acid groups or acid groups can be added to a non-ionic polymer through post- reaction modifications. For example, ethylene-methacrylic acid and sulfonated perfluorocarbon (Nafion) are synthesized through copolymerization while polystyrene sulfonate is synthesized through post-reaction modifications.
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The atomic structure derived by X-Ray powder and optical analysis of bityite is that of a two layer modification that also exhibits a complex affinity to twinning. From studies done on mica flakes from the Maantienvarsi sample, the mineral is a two layer-type modification of polytype 2M1. Bityite has a mica structure, shown in adjacent figure, which consists of tetrahedral and octahedral sheets separated by an interlayer cation. The mineral is considered a brittle mica, and it can be distinguished from the true micas by a layer charge per unit of approximately -2.0; in consequence, their interlayer cation is usually calcium or barium.
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The neutralisation of the otherwise repulsive charges of the headgroups and the absence of any steric hindrance enables strong intermolecular interactions between the acyl chains, resulting in PA-rich microdomains. Thus in vitro, physiological changes in pH, temperature, and cation concentrations have strong effects on the membrane curvature induced by PA and lysoPA. The interconversion of lysoPA, PA, and DAG - and changes in pH and cation concentration - can cause membrane bending and destabilisation, playing a direct role in membrane fission simply by virtue of their biophysical properties. However, though PA and lysoPA have been shown to affect membrane curvature in vitro; their role in vivo is unclear.
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For example, ammonia solutions have a pH greater than 7 due to the reaction NH3 \+ H+ , which decreases the hydrogen cation concentration, which increases the hydroxide ion concentration. pOH can be kept at a nearly constant value with various buffer solutions. Schematic representation of the bihydroxide ion In aqueous solution the hydroxide ion is a base in the Brønsted–Lowry sense as it can accept a protonIn this context proton is the term used for a solvated hydrogen cation from a Brønsted–Lowry acid to form a water molecule. It can also act as a Lewis base by donating a pair of electrons to a Lewis acid.
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Such a displacement only tends to be favourable when the B-site cation has an electron configuration with an empty d shell (a so-called d0 configuration), which favours energy-lowering covalent bond formation between the B-site cation and the neighbouring oxygen anions. This "d0-ness" requirement is a clear obstacle for the formation of multiferroics, since the magnetism in most transition-metal oxides arises from the presence of partially filled transition metal d shells. As a result, in most multiferroics, the ferroelectricity has a different origin. The following describes the mechanisms that are known to circumvent this contraindication between ferromagnetism and ferroelectricity.
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The non-classical description of the 2-norbornyl cation can be seen as the donation of an electron pair from a carbon-carbon sigma bond into an empty p-orbital of carbon 2. Thus this carbocation showed that sigma-bond electron donation is as plausible as pi-bond electron donation. The intense debate that followed Brown’s challenge to non-classical ion proponents also had a large impact on the field of chemistry. In order to prove or disprove the non-classical nature of the 2-norbornyl cation, chemists on both sides of the debate zealously sought out new techniques for chemical characterization and more innovative interpretations of existing data.
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Though characterization of 2-norbornyl cation crystals may have significantly precluded further debates about its electronic structure, it does not crystallize under any standard conditions. Recently, the crystal structure has been obtained and reported through a creative means: addition of aluminum tribromide to 2-norbornyl bromide in dibromomethane at low temperatures afforded crystals of [][]·. By examining the resulting crystal structure, researchers were able to confirm that the crystalline geometry best supports the case for delocalized bonding in the stable 2-norbornyl cation. Bond lengths between the "bridging" carbon 6 and each of carbons 1 and 2 were found to be slightly longer than typical alkane bonds.
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According to the nonclassical picture, one would expect a bond order between 0 and 1 for these bonds, signifying that this explains the crystal structure well. The bond length between carbons 1 and 2 was reported as being between typical single and double carbon-carbon bond lengths, which agrees with nonclassical predictions of a bond order slightly above 1. According to the non-classical picture, one would expect a bond order between 0 and 1 for the first two bonds. Investigators who crystallized the 2-norbornyl cation commented that the cation proved impossible to crystallize unless provided a chemical environment that locked it into one definite orientation.
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Langbeinites are a family of crystalline substances based on the structure of langbeinite with general formula M2M'2(SO4)3, where M is a large univalent cation such as potassium, rubidium, caesium, or ammonium), and M' is a small divalent cation for example (magnesium, calcium, manganese, iron, cobalt, nickel, copper, zinc or cadmium). The sulfate group, SO42−, can be substituted by other tetrahedral anions with a double negative charge such as tetrafluoroberyllate BeF42−, selenate (SeO42−), chromate (CrO42−), molybdate (MO42−), or tungstates. Although monofluorophosphates are predicted, they have not been described. By redistributing charges other anions with the same shape such as phosphate also form langbeinite structures.
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The second ring closure gives the bicyclic eudesmyl cation, which is stabilized by various dipole interactions, then H-2 migrates to C-3 producing a tertiary cation at C-2 (farnesyl numbering). Production of 5-epi-aristolochene from FPP by 5-epi- aristolochene 3-hydroxylase, a sesquiterpene cyclase, is considered the critical step in capsidiol biosynthesis. Aristolochene synthase enzymes from Penicillium roqueforti, Nicotiana tabacum have been purified and their crystal structures have been reported suggesting different steriochemistries for aristolochene. Penicillium roquefortis enzyme appears to synthesizes aristolochene by way of (S)-germacrene A , however, the Nicotiana tabacum enzyme 5-epi-aristolochene synthase produces the diastereoisomeric product by way of (R)-germacrene A.
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The crystal structure of ammonium perrhenate with orientationally ordered ammonium ions (blue) and ReO4 (grey) tetrahedra. The crystal structure of APR is that of scheelite, in which the atomic cation is replaced by the ammonium molecular cation. It undergoes a molecular orientational ordering transition on cooling without change of space group, but with a highly anisotropic change in the shape of the unit cell, resulting in the unusual property of having a positive temperature and pressure Re NQR coefficient. NH4ReO4 can be regarded as the prototype structure of a family of ammonium scheelites, which include the pertechnetate (NH4TcO4), periodate (NH4IO4), tetrachlorothallate (NH4TlCl4) and tetrachloroindate (NH4InCl4).
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The exact reaction mechanism is not known but could very well proceed through an arenium ion. Just as in electrophilic aromatic substitution, Activating groups such as methoxy improve yield and selectivity: Scholl Reaction Para directors Two mechanisms may compete. In step one of a radical cation mechanism a radical cation is formed from one reaction partner by oxidation, in step two the radical ion attacks the second neutral partner in a substitution reaction and a new radical ion is formed with one ring bearing the positive charge and the other one the radical position. In step three dihydrogen is split off with rearomatisation to the biaryl compound.
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Glycans may also be involved in "self" and "non self" discrimination, which may be relevant to the pathophysiology of various autoimmune diseases; including rheumatoid arthritis and type 1 diabetes. The targeting of degradative lysosomal enzymes is also accomplished by N-linked glycans. The modification of an N-linked glycan with a mannose-6-phosphate residue serves as a signal that the protein to which this glycan is attached should be moved to the lysosome. This recognition and trafficking of lysosomal enzymes by the presence of mannose-6-phosphate is accomplished by two proteins: CI-MPR (cation-independent mannose-6-phosphate receptor) and CD-MPR (cation-dependent mannose-6-phosphate receptor).
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The fluorinated carborane acid, , is even stronger than chlorinated carborane acid. It is able to protonate butane to form tert-butyl cation at room temperature and is the only known acid to protonate carbon dioxide to give the bridged cation, , making it possibly the strongest known acid. In particular, CO2 does not undergo observable protonation when treated with the mixed superacids HF-SbF5 or HSO3F-SbF5. The generic structure of a carborane acid exhibits up to three different types of substituents X, Y, and Z. The position of the acidic proton will depend on the substituents and is shown here in a generic location.
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A pseudo alum is a double sulfate of the typical formula , where A is a divalent metal ion, such as cobalt (wupatkiite), manganese (apjohnite), magnesium (pickingerite) or iron (halotrichite or feather alum), and B is a trivalent metal ion.Halotrichite on Mindat.org Double sulfates with the general formula are also known, where A is a monovalent cation such as sodium, potassium, rubidium, caesium, or thallium(I), or a compound cation such as ammonium (), methylammonium (), hydroxylammonium () or hydrazinium (), B is a trivalent metal ion, such as aluminium, chromium, titanium, manganese, vanadium, iron(III), cobalt(III), gallium, molybdenum, indium, ruthenium, rhodium, or iridium.Greenwood, N. N.; & Earnshaw, A. (1997).
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Mucolipin-1 also known as TRPML1 (transient receptor potential cation channel, mucolipin subfamily, member 1) is a protein that in humans is encoded by the MCOLN1 gene. It is a member of the small family of the TRPML channels, a subgroup of the large protein family of TRP ion channels. TRPML1 is a 65 kDa protein associated with mucolipidosis type IV. Its predicted structure includes six transmembrane domains, a transient receptor potential (TRP) cation-channel domain, and an internal channel pore. TRPML1 is believed to channel iron ions across the endosome/lysosome membrane into the cell and so its malfunction causes cellular iron deficiency.
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The oxidation of tellurium by in liquid produces the same square planar cation, in addition to the trigonal prismatic, yellow- orange : :4 Te + 3 → + :6 Te + 6 → + 2 Other tellurium Zintl cations include the polymeric and the blue-black , consisting of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with tungsten hexachloride: :8 Te + 2 → Interchalcogen cations also exist, such as (distorted cubic geometry) and . These are formed by oxidizing mixtures of tellurium and selenium with or . ;Organotellurium compounds Tellurium does not readily form analogues of alcohols and thiols, with the functional group –TeH, that are called tellurols.
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CitM is believed to transport a citrate2−-Mg2+complex in symport with one H+ per Mg2+-citrate while CitH apparently transports a citrate2−-Ca2+ complex in symport with protons. The cation specificity of CitM is: Mg2+, Mn2+, Ba2+, Ni2+, Co2+, Ca2+ and Zn2+, in this preferential order. CitM is highly specific for citrate and D-isocitrate and does not transport other di- and tri-carboxylates including succinate, L-isocitrate, cis-aconitate and tricarballylate. For CitH, the cation specificity (in order of preference) is: Ca2+, Ba2+ and Sr2+. The two proteins are 60% identical, contain about 400 amino acyl residues and possess twelve putative transmembrane spanners.
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Inorganic as well as organic ions display at moderate ionic strength I similar salt bridge association ΔG values around 5 to 6 kJ/mol for a 1:1 combination of anion and cation, almost independent of the nature (size, polarizability etc) of the ions. The ΔG values are additive and approximately a linear function of the charges, the interaction of e.g. a doubly charged phosphate anion with a single charged ammonium cation accounts for about 2x5 = 10 kJ/mol. The ΔG values depend on the ionic strength I of the solution, as described by the Debye-Hückel equation, at zero ionic strength one observes ΔG = 8 kJ/mol.
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This is also similar to CI and the difference lies in the production of a radical cation with an odd number of electrons. The reagent gas molecules are bombarded with high energy electrons and the product reagent gas ions abstract electrons from the analyte to form radical cations. The common reagent gases used for this technique are toluene, benzene, NO, Xe, Ar and He. Careful control over the selection of reagent gases and the consideration toward the difference between the resonance energy of the reagent gas radical cation and the ionization energy of the analyte can be used to control fragmentation. The reactions for charge-exchange chemical ionization are as follows.
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The amount of expansion is due largely to the type of exchangeable cation contained in the sample. The presence of sodium as the predominant exchangeable cation can result in the clay swelling to several times its original volume. Hence, sodium montmorillonite has come to be used as the major constituent in nonexplosive agents for splitting rock in natural stone quarries in an effort to limit the amount of waste, or for the demolition of concrete structures where the use of explosive charges is unacceptable. This swelling property makes montmorillonite-containing bentonite useful also as an annular seal or plug for water wells and as a protective liner for landfills.
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Electrophilic alkylating agents deliver the equivalent of an alkyl cation. Alkyl halides are typical alkylating agents. Trimethyloxonium tetrafluoroborate and triethyloxonium tetrafluoroborate are particularly strong electrophiles due to their overt positive charge and an inert leaving group (dimethyl or diethyl ether). Dimethyl sulfate is intermediate in electrophilicity.
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The dihydrogen ion is formed in nature by the interaction of cosmic rays and the hydrogen molecule. An electron is knocked off leaving the cation behind. :H2 \+ cosmic ray → + e− \+ cosmic ray. Cosmic ray particles have enough energy to ionize many molecules before coming to a stop.
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Ammonium hexafluorophosphate is the inorganic compound with the formula NH4PF6. It is a white water-soluble, hygroscopic solid. The compound is a salt consisting of the ammonium cation and hexafluorophosphate anion. It is commonly used as a source of the hexafluorophosphate anion, a weakly coordinating anion.
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Nicotinamide adenine dinucleotide is a N-alkylpyridinium cation that occurs widely in life. When the acidic proton is replaced by alkyl, the compounds are called N-alkylpyridinium. A simple representative is N-methylpyridinium ([C5H5NCH3]+). From a commercial perspective, an important pyridinium compound is the herbicide paraquat.
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Higher selectivity: for example, positive, negative and neutral substances could be separated by a reversed phase (RP)/anion-cation exchange (ACE) column in a single run. X.D. Liu, C.A. Pohl, J. Sep. Sci. 33 (2010) 779. Higher loading capacity, N.H. Davies, M.R. Euerby, D.V. McCalley, J. Chromatogr.
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1-Methylnicotinamide (trigonellamide) is a prototypic organic cation. 1-Methylnicotinamide is the methylated amide of nicotinic acid (niacin, vitamin B3). 1-Methylnicotinamide is an endogenic substance that is produced in the liver when nicotinic acid is metabolized. It is a typical substance secernated in the kidney.
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In illite, the interlayer is totally collapsed because of the presence of the poorly hydrated . Ionic potential is also a measure of the polarising power of a cation. Ionic potential could be used as a general criterion for the selection of efficient adsorbents for toxic elements.
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Endolymph is the fluid contained in the membranous labyrinth of the inner ear. The major cation in endolymph is potassium, with the values of sodium and potassium concentration in the endolymph being 0.91 mM and 154 mM, respectively. It is also called Scarpa's fluid, after Antonio Scarpa.
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Hyperpolarization-activated cyclic nucleotide–gated (HCN) channels are integral membrane proteins that serve as nonselective voltage-gated cation channels in the plasma membranes of heart and brain cells.Luthi A, McCormick DA. 1998. Neuron. H-current: properties of a neuronal and network pacemaker. Vol. 21. pp 9-12.
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Like most metals it has a close-packed crystalline structure,Russell & Lee 2005, pp. 358–60 et seq and forms a cation in aqueous solution.Harding, Janes & Johnson 2002, pp. 118 It has some properties that are unusual for a metal; taken together,Metcalfe, Williams & Castka 1974, p.
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Ternary metal hydrides have the formula AxMHn, where A+ is an alkali or alkaline earth metal cation, e.g. K+ and Mg2+. A celebrated example is K2ReH9, a salt containing two K+ ions and the ReH92− anion. Other homoleptic metal hydrides include the anions in Mg2FeH6 and Mg2NiH4.
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SkQ is a class of mitochondria-targeted antioxidants, developed by prof. Vladimir Skulachev and his team. In a broad sense, SkQ is a lipophilic cation, linked via saturated hydrocarbon chain to an antioxidant. Due to its lipophilic properties, SkQ can effectively penetrate through various cell membranes.
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Ethenium () In chemistry, ethenium, protonated ethylene or ethyl cation is a positive ion with the formula . It can be viewed as a molecule of ethylene () with one added proton (), or a molecule of ethane () minus one hydride ion (). It is a carbocation; more specifically, a nonclassical carbocation.
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1986, 108:11, pp. 3075-3077\. . This anion, which appears as a blue solution, is an eight- coordinate vanadium complex. A Ca2+ cation is often used to crystallize amavadin to obtain a good quality X-ray diffraction. Oxidized amavadin can be isolated as its PPh4+ salt.
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In 1998, MacDiarmid and Gardner finally identified the proteins responsible for the observed cation transport phenotype in Saccharomyces cerevisiae. The genes involved in this system and a second mitochondrial Mg2+ transport system, functionally identified significantly after the gene was cloned, are described in the sections below.
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Xenon forms the cation Xe(OTeF5)+.Mercier, H. P.A.; Sanders, J. C. P.; Schrobilgen, G. J. "The Hexakis(pentafluorooxotellurato)pnictate(V) Anions, M(OTeF5)6− (M = As, Sb, Bi): A Series of Very Weakly Coordinating Anions" Journal of the American Chemical Society, volume 116, 2921, (1994). .
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Figure 1. An illustration of 1- 2- and 3-dimensionality. A coordination polymer is an inorganic or organometallic polymer structure containing metal cation centers linked by ligands. More formally a coordination polymer is a coordination compound with repeating coordination entities extending in 1, 2, or 3 dimensions.
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A. californica is used to make a liniment that is a powerful pain reliever (Adams, 2012b; Fontaine et al., 2013). The monoterpenoids in the plant interact with transient receptor potential cation channels to relieve pain. The plant also contains sesquiterpenes that may be involved in pain relief.
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A silylium ion is a silicon cation with only three bonds and a positive charge. The abstraction of the silylium ion is seen from the ruthenium complex shown below.D. V. Gutsulyak, S. F. Vyboishchikov, and G. I. Nikonov, J. Am. Chem. Soc., 2010, 132, 5950. File:Nuc. Abs.
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Electron ionization mass spectrum of toluene . Note parent peak corresponding to molecular mass M = 92 (C7H8+) and highest peak at M-1 = 91 (C7H7+, quasi-stable tropylium cation). A mass spectrum is an intensity vs. m/z (mass-to-charge ratio) plot representing a chemical analysis.
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12-Crown-4 can be synthesized using a modified Williamson ether synthesis, using LiClO4 as a templating cation: : (CH2OCH2CH2Cl)2 \+ (CH2OH)2 \+ 2 NaOH → (CH2CH2O)4 \+ 2 NaCl + 2 H2O It also forms from the cyclic oligomerization of ethylene oxide in the presence of gaseous boron trifluoride.
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The divalent metal cation (magnesium) is embedded in oxygen octahedra, four from water around the equator, and two from sulfate ions at the opposite poles. In the crystal there are two different octahedral environments. Each of these octahedra are joined together by potassium ions and hydrogen bonds.
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Nitronium tetrafluoroborate is an inorganic compound with formula NO2BF4. It is a salt of nitronium cation and tetrafluoroborate anion. It is a colorless crystalline solid, which reacts with water to form the corrosive acids HF and HNO3. As such, it must be handled under water-free conditions.
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CAPB is a fatty acid amide containing a long hydrocarbon chain at one end and a polar group at the other. This allows CAPB to act as a surfactant and as a detergent. It is a zwitterion, consisting of both a quaternary ammonium cation and a carboxylate.
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Reactions of type 4 are also called acyloin rearrangements. While similar to the pinacol rearrangement, the semipinacol rearrangement differs from the pinacol rearrangement in that the cation is not formed from a vicinal 1,2-diol. With diazoalcohols the reaction is known as the Tiffeneau–Demjanov rearrangement.
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Quaternary ammonium cation. The R groups may be the same or different alkyl or aryl groups. Also, the R groups may be connected. Quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group.
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The complex Cp(CO2)Fe+(η2-vinyl ether]+ is a masked vinyl cation. Fp-R compounds are prochiral, and studies have exploited the chiral derivatives CpFe(PPh3)(CO)acyl.Karola Rück-Braun "Iron Acyl Complexes" in Transition Metals for Organic Synthesis. Vol. 1. 2nd Ed., M. Beller, C. Bolm, Eds.
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Cation exchange chromatography resolved four lethal peaks from N. a. annulata venom and six lethal peaks from N. christyi venom. The major lethal peaks (about 12% of total venom protein) were purified further with molecular sieve chromatography and were characterized as 61 (N. a. annulata toxin) and 62 (N.
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The enolate metal cation may play a large role in determining the level of stereoselectivity in the aldol reaction. Boron is often usedCowden, C. J.; Paterson, I. Org. React. 1997, 51, 1. because its bond lengths are significantly shorter than that of metals such as lithium, aluminium, or magnesium.
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One application where olation is important is leather tanning using chromium(III) sulfate. This salt dissolves to give hexaaquachromium(III) cation, [Cr(H2O)6]3+ and sulfate anions. [Cr(H2O)6]3+ acts as an acid according to the reaction:Schlesinger, M.; Paunovic, M.; Modern Electroplating. Wiley-Interscience, 4th ed.
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Kr,Kryptonium ion exist as a cation. Pm, Os, Ir, Rn, Fr, and Ra.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. .Concise Inorganic Chemistry J.D. LeeMain Group Chemistry, 2nd Edition A.G. Massey Exotic molecules such as positronium hydride have also been made.
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Delta-ruthenium-tris(bipyridine) cation Chirality is a symmetry property, not a property of any part of the periodic table. Thus many inorganic materials, molecules, and ions are chiral. Quartz is an example from the mineral kingdom. Such noncentric materials are of interest for applications in nonlinear optics.
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In the absence of divalent cation, grancalcin localizes to the cytosolic fraction; with magnesium alone, it partitions with the granule fraction; and in the presence of magnesium and calcium, it associates with both the granule and membrane fractions, suggesting a role for grancalcin in granule-membrane fusion and degranulation.
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Thus, the carbon is bonded to five boron atoms and one hydrogen atom. The cation [(PhPAu)C] contains an octahedral carbon bound to six phosphine-gold fragments. This phenomenon has been attributed to the aurophilicity of the gold ligands, which provide additional stabilization of an otherwise labile species.
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Potassium hydrosulfide is the inorganic compound with the formula KHS. This colourless salt consists of the cation K+ and the bisulfide anion [SH]−. It is the product of the half-neutralization of hydrogen sulfide with potassium hydroxide. The compound is used in the synthesis of some organosulfur compounds.
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In October 1996, he released the second single, "Body-Cation", from his upcoming album. The single charted at number 12 on the Oricon Singles chart. In December 1996, he released his concert DVD, Super Duper Vol. 5 from New York and his ninth album, La La La Love Thang.
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These excellent leaving groups, such as triflate (trifluoromethanesulfonate) and nonaflate (nonafluorobutanesulfonate), are highly prone to SN1 reactivity. Utilization of these super leaving groups allowed researchers for the first time to move beyond speculation about the existence of such vinyl cations. Vinyl cation formation through carbon-halogen bond cleavage.
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Lead telluride is a compound of lead and tellurium (PbTe). It crystallizes in the NaCl crystal structure with Pb atoms occupying the cation and Te forming the anionic lattice. It is a narrow gap semiconductor with a band gap of 0.32 eV. It occurs naturally as the mineral altaite.
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N-selectride and K-selectride are related compounds, but instead of lithium as cation they have sodium and potassium cations respectively. These reagents can sometimes be used as alternatives to, for instance, sodium amalgam reductions in inorganic chemistry. Aprepitant is another synthesis example where L-selectride was used.
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Nitrosonium tetrafluoroborate, also called nitrosyl tetrafluoroborate, is a chemical compound with the chemical formula NOBF4. This colourless solid is used in organic synthesis as a nitrosating agent. NOBF4 is the nitrosonium salt of fluoroboric acid, and is composed of a nitrosonium cation, [NO]+, and a tetrafluoroborate anion, [BF4]−.
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Water softening is achieved by percolating hard water through a bed of the sodium form of cross-linked polystyrene sulfonate. The hard ions such as calcium (Ca2+) and magnesium (Mg2+) adhere to the sulfonate groups, displacing sodium ions. The resulting solution of sodium ions is softened. cation exchange resin.
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It is not effective against Mycobacterium tuberculosis and bacterial spores. Longer expositions may inactivate some viruses. Benzododecinium bromide is an active ingredient in the trademarked antiseptic product Ajatin produced in the Czech Republic. In place of bromide, the benzododecinium cation may be used with chloride or another anion.
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M. F. Bechtold (1955): "Polymerization and Properties of Dilute Aqueous Silicic Acid from Cation Exchange". Journal of Physical Chemistry, volume 59, issue 6, pages 532–541. :H6Si2O7(aq) → 2 SiO2(s) + 3 H2O Compounds formally derived from pyrosilicic acid, such as sodium pyrosilicate, are found in the sorosilicate minerals.
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The structures of pyridine and pyridinium are almost identical. The pyridinium cation is isoelectronic with benzene. Pyridinium p-toluenesulfonate (PPTS) is an illustrative pyridinium salt; it is produced by treating pyridine with p-toluenesulfonic acid. In addition to protonation, pyridine undergoes N-centered alkylation, acylation, and N-oxidation.
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The Vilsmeier reagent is an organic compound with the formula [(CH3)2NCHCl]Cl. It is a salt consisting of the N,N-dimethyliminium cation ([(CH3)2N=CHCl]+) and chloride anion. Depending on the particular reaction, the anion can vary. In typical POCl3-based reactions, the anion is PO2Cl2−.
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Another genetic disorder associated with migraine is CADASIL syndrome or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. One meta-analysis found a protective effect from an angiotensin converting enzyme polymorphisms on migraine. The TRPM8 gene, which codes for a cation channel, has been linked to migraines.
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The constituents analyzed were normalized for a total of 100% weight combined with the calculated H2O. The weight percents for each cation in terms of oxygen are as follows: 0.63 for Na2O, 13.08 for CaO, 0.22 for SrO, 0.04 for FeO, 31.61 for As2O5, and 43.89 for V2O5.
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Richey, Herman G., Jr.; Nichols, James D.; Gassman, Paul G.; Fentiman, Allison F., Jr.; Winstein, S.; Brookhart, M.; Lustgarten, Ronald K. Classical 7-norbornenyl cation. Competition between aryl and alkenyl functions in stabilizing 7-aryl-7-norbornenyl cations. Journal of the American Chemical Society (1970), 92(12), 3783-4.
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His experiments led him to the two laws of electrochemistry. Together with Whewell, Faraday introduced the basic vocabulary for the subject, the words electrode, anode, cathode, electrolysis, electrolyte, ion, anion, and cation. They remain in standard usage. But Faraday's work was of value to more then just chemists.
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Soil amendments can also greatly increase the cation exchange capacity (CEC) of soils. Soils act as the storehouses of plant nutrients. The relative ability of soils to store one particular group of nutrients, the cations. The most common soil cations are calcium, magnesium, potassium, ammonium, hydrogen, and sodium.
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The total number of cations a soil can hold, its total negative charge, is the soil's cation exchange capacity. The higher the CEC, the higher the negative charge and the more cations that can be held and exchanged with plant roots, providing them with the nutrition they require.
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Sample proteins are first blocked by reduction and alkylation at their primary amines before endopeptidase treatment. Its negative selection method relies on strong cation exchange chromatography (SCX) to enrich for peptides representing N- and C-termini of proteins based on differences in peptide charge and pH.Chen S.-H.
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CatSper1, is a protein which in humans is encoded by the CATSPER1 gene. CatSper1 is a member of the cation channels of sperm family of protein. The four proteins in this family together form a Ca2+-permeant ion channel specific essential for the correct function of sperm cells.
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The CLC family of chloride channels contains 10 or 12 transmembrane helices. Each protein forms a single pore. It has been shown that some members of this family form homodimers. In terms of primary structure, they are unrelated to known cation channels or other types of anion channels.
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Schottky defects consist of unoccupied anion and cation sites in a stoichiometric ratio. For a simple ionic crystal of type A−B+, a Schottky defect consists of a single anion vacancy (A) and a single cation vacancy (B), or v + v following Kröger–Vink notation. For a more general crystal with formula AxBy, a Schottky cluster is formed of x vacancies of A and y vacancies of B, thus the overall stoichiometry and charge neutrality are conserved. Conceptually, a Schottky defect is generated if the crystal is expanded by one unit cell, whose a priori empty sites are filled by atoms that diffused out of the interior, thus creating vacancies in the crystal.
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Charge-transfer insulators are a class of materials predicted to be conductors following conventional band theory, but which are in fact insulators due to a charge-transfer process. Unlike Mott insulators, where the insulating properties arise from electrons hopping between unit cells, the electrons in charge-transfer insulators move between atoms within the unit cell. In the Mott–Hubbard case, it's easier for electrons to transfer between two adjacent metal sites (on-site Coulomb interaction U); in the charge-transfer case, it's easier from the anion to the metal (charge-transfer energy Δ). U is determined by repulsive/exchange effects between the cation valence electrons. Δ is tuned by the chemistry between the cation and anion.
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Transient receptor potential cation channel, subfamily V, member 3, also known as TRPV3, is a human gene encoding the protein of the same name. The TRPV3 protein belongs to a family of nonselective cation channels that function in a variety of processes, including temperature sensation and vasoregulation. The thermosensitive members of this family are expressed in subsets of human sensory neurons that terminate in the skin, and are activated at distinct physiological temperatures. This channel is activated at temperatures between 22 and 40 degrees C. The gene lies in close proximity to another family member (TRPV1) gene on chromosome 17, and the two encoded proteins are thought to associate with each other to form heteromeric channels.
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Note that unlike the allyl and benzyl carbocations (top left and right, respectively), the electron-deficient carbon of the vinyl carbocation (bottom) is double-bonded. Compared to other reactive intermediates such as radicals and carbanions, the vinyl cation long remained poorly-understood and were initially thought to be too high energy to form as reactive intermediates. Vinyl cations were first proposed in 1944 as a reactive intermediate for the acid-catalyzed hydrolysis of alkoxyacetylenes to give alkyl acetate. In the first step of their facile hydration reaction, which was the rate limiting step, a vinyl cation reactive intermediate was proposed; the positive charge was believed to formally lie on a diicoordinate carbon.
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Crystal formation can be divided into two types, where the first type of crystals are composed of a cation and anion, also known as a salt, such as sodium acetate. The second type of crystals are composed of uncharged species, for example menthol. Crystal formation can be achieved by various methods, such as: cooling, evaporation, addition of a second solvent to reduce the solubility of the solute (technique known as antisolvent or drown-out), solvent layering, sublimation, changing the cation or anion, as well as other methods. The formation of a supersaturated solution does not guarantee crystal formation, and often a seed crystal or scratching the glass is required to form nucleation sites.
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The properties of cobaltocene reported by Wilkinson and Fischer demonstrated that the unipositive cobalticinium cation [Co(C5H5)2]+ exhibited stability similar to that of ferrocene itself. This observation is not unexpected given that the cobalticinium cation and ferrocene are isoelectronic, although the bonding was not understood at the time. Nevertheless, the observation led Wilkinson and F. Albert Cotton to attempt the synthesis of rhodocenium and iridocenium salts. They reported the synthesis of numerous rhodocenium salts, including those containing the tribromide ([Rh(C5H5)2]Br3), perchlorate ([Rh(C5H5)2]ClO4), and reineckate ([Rh(C5H5)2] [Cr(NCS)4(NH3)2]·H2O) anions, and found that the addition of dipicrylamine produced a compound of composition [Rh(C5H5)2] [N(C6H2N3O6)2].
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In each case, the rhodocenium cation was found to possess high stability. Wilkinson and Fischer went on to share the 1973 Nobel Prize for Chemistry "for their pioneering work, performed independently, on the chemistry of the organometallic, so called sandwich compounds". The stability of metallocenes can be directly compared by looking at the reduction potentials of the one- electron reduction of the unipositive cation. The following data are presented relative to the saturated calomel electrode (SCE) in acetonitrile: :[Fe(C5H5)2]+ / [Fe(C5H5)2] +0.38 V :[Co(C5H5)2]+ / [Co(C5H5)2] −0.94 V :[Rh(C5H5)2]+ / [Rh(C5H5)2] −1.41 V These data clearly indicate the stability of neutral ferrocene and the cobaltocenium and rhodocenium cations.
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The triangular cation was confirmed in a reinvestigation of the mineral terlinguaite in 1989 and subsequently synthesised in a number of compounds.[Hg3]4+ Cation in Inorganic Crystal Structures, S. V. Borisov, S. A. Magarill and N. V. Pervukhina, Journal of Structural Chemistry, 44, 3, 2003, 441-447, The bonding has been described in terms of a three-center two-electron bond where overlap of the 6s orbitals on the mercury atoms gives (in D3h symmetry) a bonding "a1" orbital.Synthesis and crystal structure of the subvalent mercury cluster [triangulo- Hg3(-dmpm)4][O3SCF3]4 (dmpm = Me2PCH2PMe2), Anna Mühlecker-Knoepfler, Ernst Ellmerer-Müller, Robert Konrat, Karl-Hans Ongania, Klaus Wurst and Paul Peringer, J. Chem. Soc., Dalton Trans.
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The coordination number of each atom in this structure is 6: each cation is coordinated to 6 anions at the vertices of an octahedron, and similarly, each anion is coordinated to 6 cations at the vertices of an octahedron. The interatomic distance (distance between cation and anion, or half the unit cell length a) in some rock-salt- structure crystals are: 2.3 Å (2.3 × 10−10 m) for NaF, 2.8 Å for NaCl, and 3.2 Å for SnTe. Other compounds showing rock salt like structure are LiF,J. Aigueperse, P. Mollard, D. Devilliers, M. Chemla, R. Faron, R. Romano, J. P. Cuer, "Fluorine Compounds, Inorganic" (section 4) in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. .
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Homoaromaticity, in organic chemistry, refers to a special case of aromaticity in which conjugation is interrupted by a single sp3 hybridized carbon atom. Although this sp3 center disrupts the continuous overlap of p-orbitals, traditionally thought to be a requirement for aromaticity, considerable thermodynamic stability and many of the spectroscopic, magnetic, and chemical properties associated with aromatic compounds are still observed for such compounds. This formal discontinuity is apparently bridged by p-orbital overlap, maintaining a contiguous cycle of π electrons that is responsible for this preserved chemical stability. The homoaromatic homotropylium cation (C8H9+) The concept of homoaromaticity was pioneered by Saul Winstein in 1959, prompted by his studies of the “tris-homocyclopropenyl” cation.
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Conductivity measurements made to determine water purity will not respond to non conductive contaminants (many organic compounds fall into this category), therefore additional purity tests may be required depending on application. Sometimes, conductivity measurements are linked with other methods to increase the sensitivity of detection of specific types of ions. For example, in the boiler water technology, the boiler blowdown is continuously monitored for "cation conductivity", which is the conductivity of the water after it has been passed through a cation exchange resin. This is a sensitive method of monitoring anion impurities in the boiler water in the presence of excess cations (those of the alkalizing agent usually used for water treatment).
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Other hydrated forms, the Zundel cation , which is formed from a proton and two water molecules, and the Eigen cation , which is formed from a hydronium ion and three water molecules, are theorized to play an important role in the diffusion of protons though an aqueous solution according to the Grotthuss mechanism. Although the ion (aq) is often shown in introductory textbooks to emphasize that the hydron is never present as an unsolvated species in aqueous solution, it is somewhat misleading, as it oversimplifies infamously complex speciation of the solvated proton in water; the notation (aq) is often preferred, since it conveys aqueous solvation while remaining noncommittal with respect to the number of water molecules involved.
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All subunits are homologous to the subunits in other members of this monovalent cation (K+ or Na+):proton antiporter-3 (CPA3) family as well as subunits in the archaeal hydrogenases (TC#s 3.D.1.4.1 and 3.D.1.4.2), which share several subunits with NADH dehydrogenase subunits (3.D.1).
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Cervantine is A Hawk and a Hacksaw's fifth studio album, and the first to be released on the new label, L.M. Dupli-cation. The album's sound stands out from previous recordings, drawing a stronger influence from Greek Romani music, and the mariachi that had surrounded the group in New Mexico.
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Such behavior, called Faraday transition, is observed in the cation conductors Na2S and Li4SiO4 and anion conductors PbF2, CaF2, SrF2, SrCl2 and LaF3. Later in 1891, Johann Wilhelm Hittorf reported on the ion transport numbers in electrochemical cells, and in the early 20th century those numbers were determined for solid electrolytes.
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Mucolipin-3 also known as TRPML3 (transient receptor potential cation channel, mucolipin subfamily, member 3) is a protein that in humans is encoded by the MCOLN3 gene. It is a member of the small family of the TRPML channels, a subgroup of the large protein family of TRP ion channels.
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Alkylation of thiazoles at nitrogen forms a thiazolium cation. Thiazolium salts are catalysts in the Stetter reaction and the Benzoin condensation. Deprotonation of N-alkyl thiazolium salts give the free carbenes and transition metal carbene complexes. :Structure of thiazoles (left) and thiazolium salts (right) Alagebrium is a thiazolium-based drug.
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The ICAM binding site is on the alpha subunit. The general binding region of the alpha subunit is the I-domain. Due to the presence of a divalent cation site in the I-domain, the specific binding site is often referred to as the metal-ion dependent adhesion site (MIDAS).
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The first fluorinations of adamantane were conducted using 1-hydroxyadamantane and 1-aminoadamantane as initial compounds. Later, fluorination was achieved starting from adamantane itself. In all these cases, reaction proceeded via formation of adamantane cation which then interacted with fluorinated nucleophiles. Fluorination of adamantane with gaseous fluorine has also been reported.
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Monosodium tartrate or sodium bitartrate is a sodium acid salt of tartaric acid. As a food additive it is used as an acidity regulator and is known by the E number E335. As an analytical reagent, it can be used in a test for ammonium cation which gives a white precipitate.
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The compound crystallizes in a cubic motif called the fluorite structure. Unit cell of CaF2, known as fluorite structure, from two equivalent perspectives. The second origin is often used when visualising point defects entered on the cation. Ca2+ centres are eight-coordinate, being centered in a cube of eight F− centres.
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The cations and anions are shown by separate ternary plots. The apexes of the cation plot are calcium, magnesium and sodium plus potassium cations. The apexes of the anion plot are sulf ate , chloride and carbonate plus hydrogen carbonate anions. The two ternary plots are then projected onto a diamond.
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Treatment of this with boron trifluoride yielded [C3Ph3]BF4. :Cyclopropenium The parent cation, [C3H3]+, was reported as its hexachloroantimonate () salt in 1970. It is indefinitely stable at −20 °C. Trichlorocyclopropenium salts are generated by chloride abstraction from tetrachlorocyclopropene: :C3Cl4 \+ AlCl3 → [C3Cl3]+ Tetrachlorocyclopropene can be converted to tris(tert- butyldimethylsilyl)cyclopropene.
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Cation exchange chromatography resolved four lethal peaks from N. a. annulata venom and six lethal peaks from N. christyi venom. The major lethal peaks (about 12% of total venom protein) were purified further with molecular sieve chromatography and were characterized as 61- (N. a. annulata toxin) and 62-residue (N.
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KCC2 is a member of the cation-chloride cotransporter (CCC) superfamily of proteins. As with all CCC proteins, KCC2 is an integral membrane protein with 12 transmembrane domains and both N- and C-terminal cytoplasmic domains. The terminal cytoplasmic domains can be phosphorylated by kinases within the neuron for rapid regulation.
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They share a homologous region of about 400 residues (residues 206-623 in PKD2; residues 3656-4052 in PKD1) which includes five TMSs of both proteins. This may well be the channel domain. PKD2 and polycystin-L have been shown to exhibit voltage-, pH- and divalent cation-dependent channel activity.
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Tetrakis(hydroxymethyl)phosphonium chloride (THPC) is an organophosphorus compound with the chemical formula [P(CH2OH)4]Cl. The cation P(CH2OH)4+ is four-coordinate, as is typical for phosphonium salts. THPC has applications as a precursor to fire-retardant materials,Svara, Jürgen; Weferling, Norbert ; Hofmann, Thomas. Phosphorus Compounds, Organic.
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Several members should be stabilized taking into account a dipolar mesomeric form with for instance sesquifulvalene 4, which can be thought of as a tropylium cation joined to a cyclopentadienyl anion (both stable and aromatic). In this compound the dipolar structure is calculated to contribute 23% to the total structure.
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Benzenediazonium chloride is an organic compound with the formula [C6H5N2]Cl. It is a salt of a diazonium cation and chloride. It exists as a colourless solid that is soluble in polar solvents including water. It is the parent member of the aryldiazonium compounds, which are widely used in organic chemistry.
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However, the stability of McMurry's in-bycyclo[4.4.4]-tetradecyl cation allows the alkene to be protonated with much weaker acids as well. Even in pure acetic acid, the alkene is protonated to about 50% as determined with NMR. Hydrogen-bridged cations have been implicated in the transannular migration of hydrogens.
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These ions are known as second-generation product ions. The radical cation products are then directed towards the mass analyzer by a repeller electrode. The ionization process often follows predictable cleavage reactions that give rise to fragment ions which, following detection and signal processing, convey structural information about the analyte.
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Figure 3. Three coordination polymers of different dimensionality. All three were made using the same ligand (4,5-dihydroxybenzene-1,3-disulfonate (L)), but different metal cations. All of the metals come from Group 2 on the periodic table (alkaline earth metals) and in this case, dimensionality increases with cation size and polarizability.
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Nitronium perchlorate, NO2ClO4, also known as nitryl perchlorate and nitroxyl perchlorate, is an inorganic chemical, the salt of the perchlorate anion and the nitronium cation. It forms colorless monoclinic crystals. It is hygroscopic, and is a strong oxidizing and nitrating agent. It may become hypergolic in contact with organic materials.
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In the platensimycin crystal structure the structured water adjacent to His303 is no longer present which may suggest an alternative electronic state for this residue. A strong possibility exists that His303 would present itself as a cation capable of forming an ionic interaction with the benzoic acid group of platensimycin.
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Tetrabutylammonium tribromide, abbreviated to TBATB, is a pale orange solid with the formula [N(C4H9)4]Br3. It is a salt of the lipophilic tetrabutylammonium cation and the linear tribromide anion. The salt is sometimes used as a reagent used in organic synthesis as a conveniently weighable, solid source of bromine.
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Magnesium stearate is the chemical compound with the formula . It is a soap, consisting of salt containing two equivalents of stearate (the anion of stearic acid) and one magnesium cation (Mg2+). Magnesium stearate is a white, water-insoluble powder. Its applications exploit its softness, insolubility in many solvents, and low toxicity.
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Rieman, William, Harold F. Walton, R. Belcher, and H. Freiser (2013). Ion Exchange in Analytical Chemistry International Series of Monographs in Analytical Chemistry. Burlington: Elsevier Science. For example, in a sulphonated polystyrene resin, a cation exchange resin, the chlorine ion of a hydrochloric acid buffer should equilibrate into the resin.
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Each ion is 4-coordinate and has local tetrahedral geometry. Zinc blende is its own antitype—you can switch the anion and cation positions in the cell and it doesn't matter (as in NaCl). In fact, replacement of both the zinc and sulfur with carbon gives the diamond structure.Toreki, Rob.
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The plant's significant above-ground biomass demands the preferential uptake of nitrate over ammonia, leading to soil nitrification. It also has a high cation-exchange capacity, which also supports the larger biomass. Either of these functions could explain the increased alkalinity, but further experimentation is needed to pinpoint the exact mechanism.
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An organic cation transport protein mediates the transport of organic cations across the cell membrane. These proteins are members of the solute carrier family, subfamily 22. This family of proteins can also transport zwitterions and anions, though it is a different subfamily of solute carrier proteins than the organic anion transporters.
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An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bond to oxygen that can dissociate to produce the H+ cation and the anion of the acid.
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As with the previously described mechanisms, the heavy carbocations may at some point undergo a hydride transfer from isobutane to yield a C12 – C16 isoparaffin and a t-butyl cation. These heavy molecules tend to lower the octane and raise the boiling end point of the alkylate effluent. 2,4-dimethylpentane.
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The encoded protein is an integral protein of the plasma membrane containing 12 transmembrane segments. The first functional designation of this protein was OCTN1 ("organic cation transporter, novel, type 1"), but efficiency of transport for organic cations (e.g., tetraethylammonium) is very low. The transport efficiency for carnitine is also negligible.
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Izatt, R. et al Thermodynamic and kinetic data for cation-macrocycle interaction. Chem. Rev. vol 85 pp271-339.Sipowska, J. et al Excess enthalpies for butane and methanol at the temperatures (298.15 and 348.15) K and the pressures (5 and 15) MPa. J. Chem. Thermodyn. 1992 vol 24 pp1087-1093.
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Calcium ions play a primary role in the regulation of sperm motility. This gene belongs to a family of putative cation channels that are specific to spermatozoa and localize to the flagellum. The protein family features a single repeat with six membrane-spanning segments and a predicted calcium- selective pore region.
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Two-pore channels (TPCs) are eukaryotic intracellular voltage-gated and ligand gated cation selective ion channels. There are two known paralogs in the human genome, TPC1s and TPC2s. In humans, TPC1s are sodium selective and TPC2s conduct sodium ions, calcium ions and possibly hydrogen ions. Plant TPC1s are non-selective channels.
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When a solid solution becomes unstable—due to a lower temperature, for example—exsolution occurs and the two phases separate into distinct microscopic to megascopic lamellae. This is mainly caused by difference in cation size. Cations which have a large difference in radii are not likely to readily substitute.Nesse, William D. (2000).
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The ammonium cation is a positively charged polyatomic ion with the chemical formula . It is formed by the protonation of ammonia (NH3). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary ammonium cations (), where one or more hydrogen atoms are replaced by organic groups (indicated by R).
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Structure of N-oxoammonium salts The structure of Bobbitt's salt, an N-oxoammonium salt. N-Oxoammonium salts are a class of organic compounds with the formula [R1R2N+=O]X−. The cation [R1R2N+=O] is of interest for the dehydrogenation of alcohols. Oxoammonium salts are diamagnetic, whereas the nitroxide has a doublet ground state.
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The simple peralkyl and peraryl complexes of iron are less numerous than are the Cp and CO derivatives. One example is tetramesityldiiron. tetramesityldiiron is a rare example of a neutral per-organo complex of iron. Compounds of the type [(η3-allyl)Fe(CO)4]+X− are allyl cation synthons in allylic substitution.
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1,2- and 1,3-dithiolium cations.Dithiolium salts are compounds of the formula [(RC)3S2]+X− (R = H, alkyl, aryl, etc.). These salts consist of a planar organic cation with a variety of anions such as halides. The five-membered ring cations are observed in either of two isomers, 1,2- and 1,3-dithiolium cations.
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Four silicate tetrahedra share corners creating characteristic rings in the plane perpendicular to the c axis.Shinno, I. and Li, Z. (1998) Mössbauer studies of baotite and bafertisite. Hyperfine Interactions, 116, 189-196. The barium cation is between the rings and rutile columns, while chloride fills the void between each pair of rings.
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For the Ge(II) cryptand[2.2.2] complex, NBO analysis reveals the Ge(II) cation does not participate in any covalent bonding and that the lone pair on the Ge(II) resides in a purely s orbital, indicating a stereochemically inactive lone pair. This lone pair orbital of Ge(II) within cryptand[2.2.
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2]cryptand with two triflate counter ions. The crystal structure of this Ge cryptand[2.2.2] (CF3SO3)2 salt reveals a lack of coordination between the encapsulated Ge(II) cation and the triflate anions. Since these reports, similar cationic Ge(II) complexes have been prepared employing crown ethers, azamacrocycles, and bulky isocyanide ligands.
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The structural motif adopted by fluorite is so common that the motif is called the fluorite structure. Element substitution for the calcium cation often includes certain rare earth elements (REE), such as yttrium and cerium. Iron, sodium, and barium are also common impurities. Some fluoride anions may be replaced by the chloride anion.
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Denatonium is a quaternary ammonium cation. It is a compound of a salt with an inert anion like benzoate or saccharide. The structure of denatonium is related to the local anesthetic lidocaine, differing only by the addition of a benzyl group to the amino nitrogen. Other similar compounds are procaine and benzocaine.
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Once the normal faulting has occurred, the kerogen becomes cracked, allowing coalification to take place. Pyrite present in the system would be removed from the beds and transported by the hydrothermal fluids as the iron(II) cation with dissolved sulfur in solution. This is the source of iron in the hydrothermal fluid.
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Within the realm of bioorganometallic chemistry is the study of the fates of synthetic organometallic compounds. Tetraethyllead has received considerable attention in this regard as has its successors such as methylcyclopentadienyl manganese tricarbonyl. Methylmercury is a particularly infamous case; this cation is produced by the action of vitamin B12-related enzymes on mercury.
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P2X purinoceptor 2 is a protein that in humans is encoded by the P2RX2 gene. The product of this gene belongs to the family of purinoceptors for ATP. This receptor functions as a cation conducting ligand-gated ion channel. Binding to ATP mediates synaptic transmission between neurons and from neurons to smooth muscle.
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An azo coupling is an organic reaction between a diazonium compound and another aromatic compound that produces an azo compound. In this electrophilic aromatic substitution reaction, the aryldiazonium cation is the electrophile and the activated arene is a nucleophile. In most cases, including the examples below, the diazonium compound is also aromatic.
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Photoelectron photoion coincidence spectroscopy (PEPICO) is a combination of photoionization mass spectrometry and photoelectron spectroscopy. It is largely based on the photoelectric effect. Free molecules from a gas-phase sample are ionized by incident vacuum ultraviolet (VUV) radiation. In the ensuing photoionization, a cation and a photoelectron are formed for each sample molecule.
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The second solution has the tetrapropylammonium cation that acts as a templating agent. The third solution is the source of silica, one of the basic building blocks for the framework structure of a zeolite. Mixing the three solutions produces supersaturated tetrapropylammonium ZSM-5, which can be heated to recrystallize and produce a solid.
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Heating lead carbonate with hydrogen fluoride yields the hydrofluoride, which decomposes to the difluoride when it melts. This white crystalline powder is more soluble than the diiodide, but less than the dibromide and the dichloride. No coordinated lead fluorides exist (except the unstable PbF+ cation). The tetrafluoride, a yellow crystalline powder, is unstable.
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Many drugs are supplied as salts, with a cation and an anion. The way the INN system handles these is explained by the WHO at its "Guidance on INN" webpage. For example, amfetamine and oxacillin are INNs, whereas various salts of these compounds – e.g., amfetamine sulfate and oxacillin sodium – are modified INNs (INNM).
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It is possible that they are distant constituents of the MFS (2.A.1). The nucleobase-cation-symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Weyand et al. (2008) reported the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1 (TC# 2.A.39.3.
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It exhibits minimal sequence similarities, but similar domain organization and membrane topology with established cation channels such as the transient receptor potential (TRP) and voltage-gated ion channel (VIC) family proteins (TC# 1.A.4 and TC# 1.A.1, respectively). However, PSI-BLAST without iterations does not pick up these similarities.
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Tropylium tetrafluoroborate is an organic compound with the formula C7H7BF4. Containing the tropylium cation and the non-coordinating tetrafluoroborate counteranion, tropylium tetrafluoroborate is a rare example of a readily isolable carbocation. It is a white solid. This compound may be prepared by the reaction of cycloheptatriene with phosphorus trichloride, followed by tetrafluoroboric acid.
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At physiologic pH, chlorhexidine salts dissociate and release the positively charged chlorhexidine cation. The bactericidal effect is a result of the binding of this cationic molecule to negatively charged bacterial cell walls. At low concentrations of chlorhexidine, this results in a bacteriostatic effect; at high concentrations, membrane disruption results in cell death.
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The ion selectivity filter, pore, is formed by the complex combination of p-loops in the tetrameric protein, which are situated in the extracellular domain between the S5 and S6 transmembrane segments. As with most cation channels, TRP channels have negatively charged residues within the pore to attract the positively charged ions.
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Capsidiol is a bicyclic terpene that is biosynthetically derived from the mevalonate pathway via farnesyl pyrophosphate (FPP). The E,E-farnesyl cation is first created by the loss of pyrophosphate. Kinetic studies have indicated that turnover appears to be limited by a chemical step after the initial loss of pyrophosphate.Dewick P.M. (2002).
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The anion is tetrahedral with B-C bond lengths of approximately 1.65 Angstroms. The salt has only been obtained as the etherate, and the crystallography confirms that four ether (OEt2) molecules are bound to the lithium cation, with Li-O bond lengths of approximately 1.95 Å. The [Li(OEt2)4]+ complex is tetrahedral.
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The crown ethers are often generated in the presence of an alkali metal cation, which organizes the condensing components by complexation. An illustrative macrocyclization is the synthesis of (−)-muscone from (+)-citronellal. The 15-membered ring is generated by ring-closing metathesis. :Synthesis of muscone via RCM Uroporphyrinogen III, biosynthetic precursor to porphyrins.
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The human gene of ISLR has two alternatively spliced identical isoforms. The domains of the ISLR gene follows as: LRR_8 (leucine- rich repeat), LRR_RI (ribonuclease inhibitor), PCC (polycystin cation channel protein) Super family, and Ig (immunoglobulin). The predicted isoelectric point of unmodified protein ISLR is 5.3. The calculated molar mass is 46.0 kDa.
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The nitrogen center of pyridine features a basic lone pair of electrons. This lone pair does not overlap with the aromatic π-system ring, consequently pyridine is basic, having chemical properties similar to those of tertiary amines. Protonation gives pyridinium, C5H5NH+.The pKa of the conjugate acid (the pyridinium cation) is 5.25.
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Soil particle "hold on" to positively charged nutrient particles because they are negatively charged. The opposite charges cause the nutrients to adhere to soil particles which can then be taken up by plants.University of Minnesota Extension. 2004. Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants: Cation Exchange Capacity.
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The compound is a salt with separated hydroxyammonium and nitrate ions. Hydroxylammonium nitrate is unstable because it contains both a reducing agent (hydroxylammonium cation) and an oxidizer (nitrate), the situation being analogous to ammonium nitrate. It is usually handled as an aqueous solution. The solution is corrosive and toxic, and may be carcinogenic.
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An isodesmic crystal is a crystal in which all the bonds have the same electrostatic valency. This means that all the bonds are of the same strength. Diamonds and halite have isodesmic crystals. The opposite of an isodesmic crystal is an anisodesmic crystal, in which anions more strongly bonded to central coordinating cation.
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The dealkalization of water refers to the removal of alkalinity ions from water. Chloride cycle anion ion exchange dealkalizers remove alkalinity from water. Chloride cycle dealkalizers operate similar to sodium cycle cation water softeners. Like water softeners, dealkalizers contain ion exchange resins that are regenerated with a concentrated salt (brine) solution - NaCl.
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As a short chain fatty acid, butyric acid is fully ionized near neutral pH. In nature, the cation associated with butyrate is unknown or unimportant to the metabolizing enzymes. Butyrates are important as food for cells lining the mammalian colon (colonocytes). Without butyrates for energy, colon cells undergo autophagy (self digestion) and die.
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The concept of homoaromaticity has its origins in the debate over the non-classical carbonium ions that occurred in the 1950s. Saul Winstein, a famous proponent of the non- classical ion model, first described homoaromaticity while studying the 3-bicyclo[3.1.0]hexyl cation. Trishomoaromaticity In a series of acetolysis experiments, Winstein et al.
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The sizes are arbitrary and not necessarily similar as illustrated. The cation is coloured red and the anion is coloured blue. The green area represents solvent molecules in a primary solvation shell; secondary solvation is ignored. When both ions have a complete primary solvation sphere, the ion pair may be termed fully solvated.
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Magnesium is the eighth most abundant element on earth. It is the fourth most abundant element in vertebrates and the most abundant divalent cation within cells. The most available form of magnesium (Mg2+) for living organisms can be found in the hydrosphere. The concentration of Mg2+ in seawater is around 55 mM.
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Although studies conclude some form of coupling between the two component structures, the definite process and mechanism remains undetermined. The current agreed theory involves the conversion of niacin into 2,5-dihydropyridine through 3,6-dihydronicotinic acid. The 2,5-dihydropyridine intermediate would then react with N-methyl-Δ1-pyrrollidium cation to form enantiomerically pure (−)-nicotine.
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LiFePO4 is a 3.6V lithium-ion battery cathode initially reported by John Goodenough and is structurally related to the mineral olivine and consists of a three dimensional lattice of an [FePO4] framework surrounding a lithium cation. The lithium cation sits in a one dimensional channel along the [010] axis of the crystal structure. This alignment yields anisotropic ionic conductivity that has implications for its usage as a battery cathode and makes morphological control an important variable in its electrochemical cell rate performance. Although the iron analogue is the most commercial owing to its stability, the same composition exists for nickel, manganese, and cobalt although the observed high cell charging voltages and synthetic challenges for these materials make them viable but more difficult to commercialize.
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A Frenkel defect or dislocation defect is a type of point defect in crystalline solids named after its discoverer Yakov Frenkel. The defect forms when an atom or smaller ion (usually cation) leaves its place in the lattice, creating a vacancy, and becomes an interstitial by lodging in a nearby location. In elemental systems, they are primarily generated during particle irradiation, as their formation enthalpy is typically much higher than for other point defects, such as vacancies, and thus their equilibrium concentration according to the Boltzmann distribution is below the detection limit. In ionic crystals, which usually possess low coordination number or a considerable disparity in the sizes of the ions, this defect can be generated also spontaneously, where the smaller ion (usually the cation) is dislocated.
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Daintith, p. 968. Having published his first scientific paper in 1939 and his last in 2008, he holds the rare distinction of having authored scholarly articles in eight different decades. In 1989, he received the "James Flack Norris Award in Physical Organic Chemistry" of the American Chemical Society and in 1990 the Robert A. Welch Award in Chemistry.James Flack Norris Award in Physical Organic Chemistry, American Chemical Society Some of his major contributions include recognition of the aromatic nature of the tropylium cation and the early use of 1H NMR for the characterization of carbocations and other reactive intermediates, including heptamethylbenzenium cation, investigation of the stereochemistry of the Cope rearrangement, and pioneering work in carbene chemistry, including the discovery of dichlorocarbene.
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Me4N+ forms colorless crystals One of the most straightforward methods of preparing a simple salt containing the tetramethylammonium ion is by the reaction between trimethylamine and a methyl halide: :Me3N + Me−I → Me4N+I− [14C]-labeled TMA has been made by this method. Although this reaction is suitable for the common halides, tetramethylammonium salts with more complex anions may be prepared by salt metathesis reactions, e.g. tetramethylammonium borohydride has been made from tetramethylammonium hydroxide as shown: :Me4N+[OH]− \+ Na+[BH4]− → Me4N+[BH4]− \+ Na+ \+ HO− Although TMA salts do possess some of the phase-transfer catalytic properties that are characteristic of quaternary ammonium compounds, they tend to behave atypically because of the relatively high hydrophilicity of the TMA cation. TMA cation is hydrophilic.
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His work in this area focused on tobacco leaf extracts. In 1892 Loew observed that both calcium and magnesium can be toxic to plants when there is an excess of one and a deficiency of the other, thus suggesting there may be an optimal Ca:Mg ratio. In 1901, with D.W. May, he did further testing and suggested an ideal Ca:Mg ratio of 5 to 4, though for several species maximum growth was obtained across a wide range of ratios. This work was key to identifying the principle of cation exchange capacity and facilitating William Albrecht's later work on the Base Cation Saturation Ratio (BCSR), which is a method of interpreting soil test results that is now widely used in sustainable agriculture.
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This photoredox transformation was shown to be mechanistically distinct from another organocatalytic radical process termed singly-occupied molecular orbital (SOMO) catalysis. SOMO catalysis employs superstoichiometric ceric ammonium nitrate (CAN) to oxidize the catalytically-generated enamine to the corresponding radical cation, which can then add to a suitable coupling partner such as allyl silane. This type of mechanism is excluded for the photocatalytic alkylation reaction because whereas enamine radical cation was observed to cyclize onto pendant olefins and open cyclopropane radical clocks in SOMO catalysis, these structures were unreactive in the photoredox reaction. Diagram of Enantioselective Alkylation of Aldehydes via the synergistic combination of organo- and photoredox catalysis This transformation include alkylations with other classes of activated alkyl halides of synthetic interest.
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Capsaicin and RTX, elicit burning pain by activating a non-selective cation channel expressed on sensory nerve endings. When capsaicin was found to have analgesic effects in preclinical studies much emphasis was put into the research of the receptor/channel that capsaicin binds to and activates. Besides being activated by capsaicin, TRPV1 also responds to a wide range of exogenous and endogenous chemical ligands as well as physical stimuli such as heat over 42 °C and changes in more diverse activators such as protons (acid, pH<6). TRPV1 is also subject to regulation by changes in membrane potential and this intrinsic voltage-dependence is thought to underlie the gating mechanism of this non-selective cation channel which leads to the influx of sodium and calcium ions.
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Depending on the exact substrate, alkyne hydrohalogenation can proceed though a concerted protonation/nucleophilic attack (AdE3) or stepwise by first protonating the alkyne to form a vinyl cation, followed by attack of HX/X- to give the product (AdE2) (see electrophile for arrow pushing). As in the case of alkenes, the regioselectivity is determined by the relative ability of the carbon atoms to stabilize positive charge (either a partial charge in the case of a concerted transition state or a full formal charge for a discrete vinyl cation). Depending on reaction conditions, the main product could be this initially formed alkenyl halide, or the product of twice hydrohalogenation to form a dihaloalkane. In most cases, the main regioisomer formed is the gem- dihaloalkane.
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Both involve the use of a strong acid to form a linear 3 center-2 electron bond. Scheme 2 - Final steps in the synthesis of (a) 1,6-dimethyl-1-cyclodecyl cation, first characterized by T.S. Sorensen in 1978 and (b) the in-bicyclo[4.4.4]-1-tetradecyl cation which J. E. McMurry synthesized in 1992. Both involve the use of a strong acid to form a linear 3 center-2 electron bond. In both cases, the final step used an extremely strong acid to form a carbocation across the molecule from the hydrogen to be bridged. In Sorensen's use of fluorosulfonic acid, a hydroxyl group leaves to form a tertiary carbocation. With TFA, an alkene is protonated, again causing the creation of the carbocation bridgehead.
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Sodium chloride (also known as common salt) is the principal source of sodium in the diet, and is used as seasoning and preservative, such as for pickling and jerky; most of it comes from processed foods. The Dietary Reference Intake for sodium is 1.5 grams per day, but most people in the United States consume more than 2.3 grams per day, the minimum amount that promotes hypertension; this in turn causes 7.6 million premature deaths worldwide. Potassium is the major cation (positive ion) inside animal cells, while sodium is the major cation outside animal cells. The concentration differences of these charged particles causes a difference in electric potential between the inside and outside of cells, known as the membrane potential.
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The biosynthesis of thujone is similar to the synthesis of other monoterpenes and begins with the formation of geranyl diphosphate (GPP) from Dimethylallyl pyrophosphate (DMAPP) and isopentenyl diphosphate (IPP), catalyzed by the enzyme geranyl diphosphate synthase. Quantitative 13CNMR spectroscopic analysis has demonstrated that the isoprene units used to form thujone in plants are derived from the methylerythritol phosphate pathway (MEP). The reactions that generate the thujane skeleton in sabinene from GPP are mediated by the enzyme sabinene synthase which has GPP as its substrate. GPP (1) first isomerizes to linalyl diphosphate (LPP) (2) and neryl diphosphate (NPP) (3). LPP preferentially forms a delocalized allylic cation-diphosphate (4). The ion-pair intermediate then cyclizes in an electrophilic addition to yield the α-terpinyl tertiary cation (5).
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The electronic environment of two iron bearing minerals in the lower mantle (bridgmanite, ferropericlase) transitions from a high-spin (HS) to a low-spin (LS) state. Fe2+ in ferropericlase undergoes the transition between 50-90 GPa. Bridgmanite contains both Fe3+ and Fe2+ in the structure, the Fe2+ occupy the A-site and transition to a LS state at 120 GPa. While Fe3+ occupy both A- and B-sites, the B-site Fe3+ undergoes HS to LS transition at 30-70 GPa while the A-site Fe3+ exchanges with the B-site Al3+ cation and becomes LS. This spin transition of the iron cation results in the increase in partition coefficient between ferropericlase and bridgmanite to 10-14 depleting bridgmanite and enriching ferropericlase of Fe2+.
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Commercially available, this compound may be prepared by oxidizing ferrocene with ferric salts followed by addition of hexafluorophosphoric acid. The compound has been characterized by X-ray crystallography. The cation and anion are well separated. The average Fc-C bond lengths is 2.047 Å, which is virtually indistinguishable from the Fe-C distance in ferrocene.
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Transient receptor potential cation channel, subfamily C, member 6, also known as TRPC6, is a human gene encoding a protein of the same name. TRPC6 is a transient receptor potential channel of the classical TRPC subfamily. It has been associated with depression and anxiety (see below), as well as with focal segmental glomerulosclerosis (FSGS).
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Aromatic hydrocarbons show distinct molecular ion peak.benzylic cleavage is pretty common. When alkyl groups are attached to the ring, a favorable mode of cleavage is to lose a H-radical to form the tropylium cation (m/z 91). Benzylic cleavage Alkyl substituted benzenes can fragment via the kinetic controlled process to form C6H5+, C6H6+ ions.
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Certain mutations, like GLY286ASP and a 3-bp deletion in ILE435/436, cause Stomatin-deficient cryohydrocytosis with neurologic defects (SDCHCN), a rare form of stomatocytosis characterized by episodic hemolytic anemia, cold-induced red cells cation leak, erratic hyperkalemia, neonatal hyperbilirubinemia, hepatosplenomegaly, cataracts, seizures, mental retardation, and movement disorder. Inheritance of this disease is autosomal dominant.
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Ma Y, Li ZZ, Zhang KX. Identifi cation of HIV infection among drug users in China. Zhonghua Liu Xing Bing Xue Za Zhi 1990; 11:184–85 (in Chinese). Yunnan is the area most affected by HIV/AIDS in China. In 1989 first infections appeared among needle sharing drug users near the Burmese border.
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It desensitizes to a small conductance in continuous light. Recovery from desensitization is accelerated by extracellular H+ and a negative membrane potential. It may be a photoreceptor for dark adapted cells. A transient increase in hydration of transmembrane α-helices with a t(1/2) = 60 μs tallies with the onset of cation permeation.
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In solution, lead(II) hydroxide is a somewhat weak base, forming lead(II) ion, Pb2+, under weakly acidic conditions. This cation hydrolyzes and, under progressively increasing alkaline conditions, forms Pb(OH)+, Pb(OH)2(aqueous), Pb(OH)3−, and other species, including several polynuclear species, e.g., Pb4(OH)44+, Pb3(OH)42+, Pb6O(OH)64+.
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More recent studies that specifically set out to test the influence of cation ratios on nutrition are less encouraging. A three-year field study performed by Mark Schonbeck Schonbeck, M. 2000. Balancing soil nutrients in organic vegetable production systems: Testing Albrecht's base saturation theory in southeastern soils. Organic Farming Res. Found. Inf. Bull. 10:17.
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Action potentials can also involve calcium (Ca2+),Bullock, Orkand, and Grinnell, pp. 153–54. which is a divalent cation that carries a double positive charge. The chloride anion (Cl−) plays a major role in the action potentials of some algae, but plays a negligible role in the action potentials of most animals.Schmidt-Nielsen, p. 483.
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Low-energy σ-donation orbitals from the base to boron are present in these compounds, and the π-interaction from boron's lone pair to the Lewis base serves as the HOMO. Calculated electronic structure for a number of borylene complexes were compared with their isoelectronic homologues: carbone complexes (CL2) and nitrogen cation complexes ((N+)L2).
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The term "active" represents a ratio of the cation-exchange capacity to clay of the pedon. The term "mesic" indicates the soil developed in a temperature between 8 and 15 degrees C. The "Typic Dystrudepts" are typical profiles [typic] with low pH [dystr] with an udic moisture regime and are within the Inceptisol order [epts].
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The mechanism of the SHJ reaction begins with the formation of the key cyclic cation 1. Nucleophilic attack at the anomeric position by the most nucleophilic nitrogen (N1) then occurs, yielding the desired β-nucleoside 2.Choi, W-B.; Wilson, L. J.; Yeola, S.; Liotta, D. C.; Schinazi, R. F. J. Am. Chem. Soc.
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An alternative or simultaneous reaction is the substitution of Cl− with Br− about the Au(III) center. Both complexation with the ammonium cation and/or speciation of the Au(III) precursor influence the kinetics of the nanoparticle formation reaction and therefore influence the size, shape, and (size and shape) distributions of the resulting particles.
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300px Figure 2. Generalized pathway for the synthesis of sesquiterpenes. Farnesyl diphosphate is the universal precursor to a wide variety of linear and cyclized sesquiterpenes. Of particular interest to juvabione biosynthesis (Scheme 1), dissociation of the terminal diphosphate from the FPP precursor generates the (E,E)-farnesyl allylic cation, leading to nerolidyl diphosphate (NPP).
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Maricite is an ionic double metal phosphate, with a space filling capacity of about 70% (Le Page, and Donnay, 1977). The structure of maricite contains a sodium cation enclosed by ten oxygen anions within 10 Å, in an irregular coordination. There is (2+2+2) type distorted tetrahedron around the iron (Bridson, et al., 1997).
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Part of that intracellular increase comes from calcium released from intracellular stores and another part comes from transmembrane calcium influx, through both calcium-sensitive chloride channels and voltage-independent cation channels permeable to calcium. Moreover, it has been suggested that an extracellular calcium-sensing receptor (CaSR) also contributes to the rise in intracellular calcium concentration.
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As expected, teleosts (bony fish) are not repelled by the electropositive metal's cation liberation in seawater. This is because teleosts lack the ampullae of Lorenzini. Teleost response was confirmed using captive Cobia (Rachycentron canadum) and Pacific halibut (Hippoglossus stenolepis). In July 2008 swordfish (Xiphias gladius) catch was reported on experimental hooks treated with electropositive metal.
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According to IUPAC nomenclature of organic chemistry, the hydronium ion should be referred to as oxonium. Hydroxonium may also be used unambiguously to identify it. A draft IUPAC proposal also recommends the use of oxonium and oxidanium in organic and inorganic chemistry contexts, respectively. An oxonium ion is any ion with a trivalent oxygen cation.
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Dilute solutions dissociate according to the following equilibrium: :PCl5 \+ Cl− At higher concentrations, a second equilibrium becomes more prevalent: :2 PCl5 \+ The cation and the anion are tetrahedral and octahedral, respectively. At one time, PCl5 in solution was thought to form a dimeric structure, P2Cl10, but this suggestion is not supported by Raman spectroscopic measurements.
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Albumin constitutes about 60% of the total protein in plasma and is present at concentrations between 35 and 55 mg/mL.Shen, Y., Jacobs, J. M., et al. 2004. "Ultra-High-Efficiency Strong Cation Exchange LC/RPLC/MS/MS for High Dynamic Range Characterization of the Human Plasma Proteome". Anal Chem. Vol. 76. pp. 1134-1144.
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S-Adenosyl- methionine is a cofactor derived from methionine. The methionine-derivative S-adenosyl methionine (SAM) is a cofactor that serves mainly as a methyl donor. SAM is composed of an adenosyl molecule (via 5' carbon) attached to the sulfur of methionine, therefore making it a sulfonium cation (i.e., three substituents and positive charge).
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The quaternary ammonium cation in some formulations is didecyldimethylammonium (DDA) . DDA is commercially produced as the carbonate, under the trade name "Carboquat". The carbonate is used instead of the chloride to reduce corrosion of the treatment equipment. DDA carbonate is non- volatile and highly soluble in water, with near zero octanol-water partition coefficient.
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The iminium cation [(CH3)2NC=HCl]+ is the reactive component of interest. This iminium species is a derivative of the imidoyl chloride CH3N=CHCl. Analogues of this particular reagent are generated when tertiary amides other than DMF are treated with POCl3. The salt is a white solid that is soluble in polar organic solvents.
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Following this discovery, other fundamental structures such as the Wells–Dawson ion were found, and their chemistry and applications as catalysts were determined. Ramazzoite, the first example of a mineral with a polyoxometalate cation, was discovered in 2016 in Mt. Ramazzo Mine, Liguria, Italy. This polyoxometalate has not been reported in a synthetic compound.
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Under similar conditions, the selectivity of CrPO4 for dative cations follows the sequence: Pb2+ > Cu2+ > Ni2+ ≅ Cd2+. Increases in temperature and pH enhances the ion exchange reaction. Chromium(III) phosphate is also used to catalyze cation exchange in sorption reactions. This catalysis is widely used in the reduction of metal toxicity during environmental clean-ups.
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Sulfonium ion A sulfonium ion, also known as sulphonium ion or sulfanium ion, is a positively charged ion (a "cation") featuring three organic substituents attached to sulfur. These organosulfur compounds have the formula [SR3]+. Together with a negatively charged counterion, they give sulfonium salts. They are typically colorless solids that are soluble in organic solvent.
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Ammonium triiodide (NH4I3) is the salt of the ammonium cation with the triiodide anion. It is a very unstable compound and very easily ignited just by touch. Sometimes the name ammonium triiodide is mistakenly used to refer to a different compound, nitrogen triiodide (NI3), or more precisely, the slightly more stable ammine, NI3 · NH3.
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The multivalent vanadium cation (V3+<->V5+) plays an important role to accomplish the multi-electron reactions. These promising materials shine lights on the battery industry to increase energy density rapidly. He received the Young Author Award from The Electrochemical Society in 1971, the Battery Research Award in 2003, and was elected a Fellow in 2004.
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The thallium(I) halides are stable. In keeping with the large size of the Tl+ cation, the chloride and bromide have the caesium chloride structure, while the fluoride and iodide have distorted sodium chloride structures. Like the analogous silver compounds, TlCl, TlBr, and TlI are photosensitive and display poor solubility in water.Greenwood and Earnshaw, p.
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The salt is produced by hydrolysis of zirconium tetrachloride or treating zirconium oxide with hydrochloric acid.Ralph Nielsen "Zirconium and Zirconium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. It adopts a tetrameric structure, consisting of the cation [Zr4(OH)8]8+. features four pairs of hydroxide bridging ligands linking four Zr4+ centers.
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This species has a quadruple bond between the two tungsten centers. Related quadruply bonded complexes include [W2Cl8]4− and [Mo2Cl8]4−. Because of its low ionization energy, W2(hpp)4 is easily oxidized back to the dichloride by dichloromethane. It is readily oxidized to the corresponding cation with the oxidants fullerene and with tetracyanoquinodimethane.
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Calcium caseinate is one of several milk proteins derived from casein in skim and 1% milk. Calcium caseinate is primarily used in meal preparation and fat breakdown. Caseinates are produced by adding an alkali to another derivative of casein, acid casein. The type of caseinate is determined by the cation added alongside the acid casein.
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At the top of this pyramid, there resides a carbon atom, still connected to a hydrogen. The original expected structure turned out to be not even close to an energy minimum: it represented a maximum. :Figure 1: Several possibilities for (CH)5 cation. :500px : 1a starting situation in the calculations: the chloride ion just left.
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Tetrabutylammonium hexafluorophosphate is a salt with the formula NBu4PF6. It is a white powder that is used as an electrolyte in nonaqueous electrochemistry. It is highly soluble in polar organic solvents such as acetone and acetonitrile. The salt consists of a positively charged tetrabutylammonium, a quaternary ammonia cation and a weakly basic hexafluorophosphate anion.
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Large cation/anion ion exchangers used in demineralization of boiler feedwater. Feed water for boilers needs to be as pure as possible with a minimum of suspended solids and dissolved impurities which cause corrosion, foaming and water carryover. The most common options for demineralization of boiler feedwater are reverse osmosis (RO) and ion exchange (IX).
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In 1929, Pauling published five rules which help to predict and explain crystal structures of ionic compounds. These rules concern (1) the ratio of cation radius to anion radius, (2) the electrostatic bond strength, (3) the sharing of polyhedron corners, edges and faces, (4) crystals containing different cations, and (5) the rule of parsimony.
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Euphorbia resinifera contains a milky fluid or latex, which in its dried form is called Euphorbium. It has high concentration of resiniferatoxin, an analog of capsaicin, the primary vanilloid compound found in hot peppers. It can interact with a vanilloid receptor on primary sensory neurons mediating pain (nociception) and neurogenic inflammation. The pain sensing cation channel is TRPV1.
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In 2010, Barnes and Trost started their own label, L.M. Dupli-cation, and released their fifth album, Cervantine, in February 2011. It features guest performances from Stephanie and Chris Hladowski. A Hawk and A Hacksaw have appeared at the Roskilde Festival, The Green Man Festival, Pitchfork Music Festival, The Calgary Folk Fest, Wellington Arts Fest (N.Z.), among others.
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Hydrazine can be monoprotonated to form various solid salts of the hydrazinium cation (N2H5+) by treatment with mineral acids. A common salt is hydrazinium sulfate, [N2H5]HSO4, also called hydrazine sulfate. Hydrazine sulfate was investigated as a treatment of cancer-induced cachexia, but proved ineffective. Double protonation gives the hydrazinium dication (H3NNH32+), of which various salts are known.
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The ground state molecular geometry of tricarbon has been identified as linear via its characteristic symmetric and antisymmetric stretching and bending vibrational modes and bears bond lengths of 129 to 130 picometer corresponding to those of alkenes. The ionization potential is determined experimentally at 11 to 13.5 electronvolts. In contrast to the linear tricarbon molecule, the cation is bent.
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Lanosterol synthase is an oxidosqualene cyclase (OSC) enzyme that converts (S)-2,3-oxidosqualene to a protosterol cation and finally to lanosterol. Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene. In eukaryotes, lanosterol synthase is an integral monotopic protein associated with the cytosolic side of the endoplasmic reticulum.
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Sodium hexachloroplatinate, the sodium salt of chloroplatinic acid, is an inorganic compound with the formula Na2[PtCl6], consisting of the sodium cation and the hexachloroplatinate anion. As explained by Cox and Peters, anhydrous sodium hexachloroplatinate, which is yellow, tends to form the orange hexahydrate upon storage in humid air. The latter can be dehydrated upon heating at 110 ºC.
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A slurry of resin, such as DEAE- Sephadex is poured into the column. The matrix that is used is insoluble with charged groups that are covalently attached. These charged groups are referred to as exchangers like cation and anion exchangers. After it settles, the column is pre-equilibrated in buffer before the protein mixture is applied.
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Ferrocene is also a structurally unusual scaffold as illustrated by the popularity of ligands such as 1,1'-bis(diphenylphosphino)ferrocene, which are useful in catalysis.Petr Stepnicka "Ferrocenes: Ligands, Materials and Biomolecules" J. Wiley, Hoboken, 2008. Treatment of ferrocene with aluminium trichloride and benzene gives the cation [CpFe(C6H6)]+. Oxidation of ferrocene gives the blue 17e species ferrocenium.
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The xenonium ion, XeH+, is an onium compound, consisting of protonated xenon. Although the existence of the xenonium cation itself has not been proven, salts of the fluoroxenonium ion, XeF+, are known to exist, for instance fluoroxenonium pentafluoroplatinate (XeFPtF5), more commonly known as xenon hexafluoroplatinate.Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. .
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14 The significance of this structural property will be explained further by coordination polyhedra. The second substitution occurs between Na+ and Ca2+; however, the difference in charge has to accounted for by making a second substitution of Si4+ by Al3+., p. 585 Coordination polyhedra are geometric representations of how a cation is surrounded by an anion.
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In the second half-reaction of SQS, presqualene pyrophosphate (PSPP) moves to a second reaction site within SQS. Keeping PSPP in the central channel of SQS is thought to protect the reactive intermediate from reacting with water. From PSPP, squalene is formed by a series of carbocation rearrangements. The process begins with ionization of pyrophosphate, giving a cyclopropylcarbinyl cation.
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Electron separation energy or electron binding energy, the energy required to remove one electron from a neutral atom or molecule (or cation) is called ionization energy. The reaction leads to photoionization, photodissociation, the photoelectric effect, photovoltaics, etc. Bond-dissociation energy is the energy required to break one bond of a molecule or ion, usually separating an atom or atoms.
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Binding energy (in kcal/mol) for Na+ to benzene with prototypical substituents. The electronic properties of the substituents also influence the strength of the attraction. Electron withdrawing groups (for example, cyano −CN) weaken the interaction, while electron donating substituents (for example, amino −NH2) strengthen the cation–π binding. This relationship is illustrated quantitatively in the margin for several substituents.
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Members of the RTX toxin family display a large range of functions, and typically multiple functional domains. Pore-formation is the only known shared function in RTX cytotoxins, and pores are typically cation- selective allowing for an influx of Ca2+ in target cells. Members of the RTX superfamily (RTX (TC# 1.C.11); HrpZ (TC# 1.
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This channel probably delivers the N-terminal adenylate cyclase to the host cell cytoplasm. Mutations in residues in an amphipathic α-helix (Glu509 and Glu516) in the pore-forming domain block adenylate cyclase translocation and modulate cation selectivity of the membrane channel. ACT does not use a protein receptor and inserts into liposomes. Phosphatidylethanolamine and cholesterol stimulate ACT insertion.
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The product of this gene belongs to the family of transient receptor potential (TRP) channels. TRP channels are cation-selective channels important for cellular calcium signaling and homeostasis. The protein encoded by this gene mediates calcium entry, and this entry is potentiated by calcium store depletion. Alternatively spliced transcript variants encoding different isoforms have been -identified.
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Although TRPV2 is a nonspecific cation channel, it is more permeable to calcium ions; calcium is an intracellular messenger and plays a very important role in a variety of different cellular processes. At rest, the pore channel is closed; in the activated state, the channel opens, allowing the influx of sodium and calcium ions that initiates an action potential.
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In molecular biology, the sea anemone cytotoxic proteins are lethal pore- forming proteins, known collectively as actinoporins, a sub-class of cytolysins. There are several different groups of cytolysins based on their structure and function. This entry represents the most numerous group, the 20kDa highly basic peptides. These cytolysins form cation-selective pores in sphingomyelin-containing membranes.
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Glycated hemoglobin is preferred over glycosylated hemoglobin to reflect the correct (non-enyzmatic) process. Early literature often used glycosylated as it was unclear which process was involved until further research was performed. The terms are still sometimes used interchangeably in English-language literature. The naming of HbA1c derives from Hemoglobin type A being separated on cation exchange chromatography.
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Formation of an adduct of ammonia and boron trifluoride, involving formation of a coordinate covalent bond. Coordinate covalent bonding is pervasive. In all metal aquo- complexes [M(H2O)n]m+, the bonding between water and the metal cation is described as a coordinate covalent bond. Metal-ligand interactions in most organometallic compounds and most coordination compounds are described similarly.
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Corderoite has crankshaft chains that are crosswise linked by additional Hg²+. The bond distance between the cation Hg and anion S is 2.422 Angstroms. It has two angles, Hg-S-HG= 94.1º and S-Hg-S= 165.1º. Various sulfide halides of Hg share the feature of being face-sharing [HgS2X4] −6 polyhedral, as corderoite's polyhedra X=Cl.
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Many polycyclic aromatic hydrocarbon diolepoxides and their precursor diols and epoxides are tumorigenic in animals. The radical cation mechanism involves generation of unstable adducts at G and A, leading to apurinic sites and mutations in HRAS. Orthoquinone formation could lead to stable and unstable DNA adducts and generation of reactive oxygen species, inducing mutations in P53.K.Straif et al.
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The unpleasant smell of diallyl disulfide is perceived through the transient receptor potential cation channel, member A1 (TRPA1). This ion channel had long been present not only in humans and animals, but even in fungi. Thus, Alliaceae plants have likely developed the diallyl disulfide-TRPA1 protection mechanism against predators at the early stages of the evolution.
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The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. A hydroxide attached to a strongly electropositive center may itself ionize, liberating a hydrogen cation (H+), making the parent compound an acid. The corresponding electrically neutral compound HO• is the hydroxyl radical.
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Gossypol is a terpenoid aldehyde which is formed metabolically through acetate via the isoprenoid pathway. The sesquiterpene dimer undergoes a radical coupling reaction to form gossypol. The biosynthesis begins when geranyl pyrophosphate (GPP) and isopentenyl pyrophosphate (IPP) are combined to make the sesquiterpene precursor farnesyl diphosphate (FPP). The cadinyl cation (1) is oxidized to 2 by (+)-δ-cadinene synthase.
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Other studies on the stability of the 2-norbornyl cation have shown that the alkyl substitutions at carbon 1 or 2 force the system to be decidedly classical. Tertiary carbocations are much more stable than their secondary counterparts and therefore do not need to adopt delocalized bonding in order to reach the lowest possible potential energy.
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The protein encoded by this gene belongs to the family of P-type cation transport ATPases. This gene encodes a catalytic subunit of the ouabain- sensitive H+/K+ -ATPase that catalyzes the hydrolysis of ATP coupled with the exchange of H+ and K+ ions across the plasma membrane. It is also responsible for potassium absorption in various tissues.
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Hyperforin and adhyperforin are wide-spectrum inhibitors of the reuptake of serotonin, norepinephrine, dopamine, glutamate, GABA, glycine, and choline, and they exert these effects by binding to and activating the transient receptor potential cation channel TRPC6. Activation of TRPC6 induces the entry of calcium (Ca2+) and sodium (Na+) into the cell, which causes the effect through unknown mechanism.
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An Alisol is a Reference Soil Group of the World Reference Base for Soil Resources (WRB). Alisols have an argic horizon, which has a high cation exchange capacity. In the subsoil, the base saturation is low. There exist mixed forms, for example 'Stagnic Alisol', that are mainly Alisol, but also contain components that are found in Stagnosols.
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The Polycystin Cation Channel (PCC) Family (TC# 1.A.5) consists of several transporters ranging in size from 500 to over 4000 amino acyl residues (aas) in length and exhibiting between 5 and 18 transmembrane segments (TMSs). This family is a constituent of the Voltage-Gated Ion Channel (VIC) Superfamily. These transporters generally catalyze the export of cations.
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Aside from protons, other electrophilic groups can attack an acetylene moiety. When attacked by carboxylic acids, cis/trans alkene adducts may be formed. The reaction with hydrogen halides, which also has an initial protonation step, results in the formation of halo-substituted alkenes. Lastly, adamantyl ketones may be formed from an adamantyl cation attack on acetylene and subsequent hydration.
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If farms are unable to provide separate diets for far-off and close-up cows, producers may chose to manage their diets with a shorter dry period and a negative DCAD (dietary cation-anion difference) ration diet. These diets are acidic and help calcium be reabsorbed within the cows body and reduce the risk of milk fever.
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Cetrimonium bromide ([(C16H33)N(CH3)3]Br; cetyltrimethylammonium bromide; hexadecyltrimethylammonium bromide; CTAB) is a quaternary ammonium surfactant. It is one of the components of the topical antiseptic cetrimide. The cetrimonium (hexadecyltrimethylammonium) cation is an effective antiseptic agent against bacteria and fungi. It is also one of the main components of some buffers for the extraction of DNA.
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399 Liquid germanium is a metallic conductor, with an electrical conductivity similar to that of liquid mercury.Berger 1997, pp. 71–2 Most of the chemistry of germanium is characteristic of a nonmetal.Jolly 1966, pp. 125–6 Whether or not germanium forms a cation is unclear, aside from the reported existence of the Ge2+ ion in a few esoteric compounds.
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An example of a fluorocarbonate: bastnäsite from Zagi Mountain, Federally Administered Tribal Areas, Pakistan. Size: 1.5×1.5×0.3 cm. A carbonate fluoride, fluoride carbonate, fluorocarbonate or fluocarbonate is a double salt containing both carbonate and fluoride. The salts are usually insoluble in water, can can have more than one kind of metal cation to make more complex compounds.
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Lipophilic cation determines the efficiency of penetration through the membranes into the mitochondrial matrix. The best properties are shown by SkQ-compounds with triphenylphosphonium ion (TPP): MitoQ, SkQ1, and others. Similar penetration efficiency was shown for compounds with rhodamine 19, such as SkQR1. Rhodamine has fluorescence properties, so its derivatives are used in the visualization of mitochondria.
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The pure (β) form of cobalt(II) hydroxide has the brucite crystal structure. As such, the anion and cation packing are like those in cadmium iodide, in which the cobalt(II) cations have octahedral molecular geometry. The beta form can be obtained as platelets with partial hexagonal geometry, 100-300 nm wide and 5-10 nm thick.
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Because of its solvatochromic properties MOED, and solvatochromic dyes in general, are useful as solvent polarity indicators, and for creating solutions that absorb light at a specific frequency. Additional potential areas of use include pH sensors and transition metal cation indicators. Further uses of MOED includes the production of certain photosensitive materials. Research into merocyanine dyes is ongoing.
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Within this stretch is found PLGP, an amino acid sequence typical of collagenase substrates. This sequence may thus be implicated in self-processing of the collagenase. Metalloproteases are the most diverse of the seven main types of protease, with more than 50 families identified to date. In these enzymes, a divalent cation, usually zinc, activates the water molecule.
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Tetraethylammonium ('TEA), (') or (Et4N+) is a quaternary ammonium cation consisting of four ethyl groups attached to a central nitrogen atom, and is positively charged. It is a counterion used in the research laboratory to prepare lipophilic salts of inorganic anions. It is used similarly to tetrabutylammonium, the difference being that its salts are less lipophilic and more easily crystallized.
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This waxy white solid reacts vigorously with water. With metal cations, phosphate forms a variety of salts. These solids are polymeric, featuring P-O-M linkages. When the metal cation has a charge of 2+ or 3+, the salts are generally insoluble, hence they exist as common minerals. Many phosphate salts are derived from hydrogen phosphate (HPO42−).
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In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation , the type of oxonium ion produced by protonation of water. It is the positive ion present when an Arrhenius acid is dissolved in water, as Arrhenius acid molecules in solution give up a proton (a positive hydrogen ion, ) to the surrounding water molecules ().
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Lithium borohydride is a stronger reducing agent than sodium borohydride. In mixtures of methanol and diethyl ether, lithium borohydride is able to reduce esters to alcohols and primary amides to amines. In contrast, these substrates are unaffected by sodium borohydride. The enhanced reactivity is attributed to the polarization of the carbonyl substrate by complexation to the lithium cation.
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3, p. 323-334; Génin J.-M. R., Aïssa R., Géhin A., Abdelmoula M., Benali O., Ernstsen V., Ona-Nguema G., Upadhyay Ch. and Ruby Ch.; 2005: Fougerite and FeII-III hydroxycarbonate green rust; ordering, deprotonation and/or cation substitution; structure of hydrotalcite-like compounds and mythic ferrosic hydroxide Fe(OH)2+x, Solid State Sciences, vol. 7., no.
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Another molybdenum telluride has formula Mo2Te3. Yet another molybdenum telluride, called hexamolybdenum octatelluride Mo6Te8 forms black crystals shaped like cubes. It is formed when the elements in the correct ratio are heated together at 1000 °C for a week. It is related to the Chevrel phases, but without an extra metallic cation, however it is not superconducting.
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In the case of dialkyl- substituted alkynes (e.g., 3-hexyne), the intermediate vinyl cation that would result from this process is highly unstable. In such cases, the simultaneous protonation (by HCl) and attack of the alkyne by the nucleophile (Cl−) is believed to take place. This mechanistic pathway is known by the Ingold label AdE3 ("addition, electrophilic, third-order").
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Unlike its lighter neighbors, cadmium and zinc, mercury usually forms simple stable compounds with metal-metal bonds. Most mercury(I) compounds are diamagnetic and feature the dimeric cation, Hg. Stable derivatives include the chloride and nitrate. Treatment of Hg(I) compounds complexation with strong ligands such as sulfide, cyanide, etc. induces disproportionation to and elemental mercury.
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The selenide iodides are chemical compounds that contain both selenide ions (Se2−) and iodide ions (I−) and one or metal atoms. They are in the class of mixed anion compounds or chalcogenide halides. Some related compounds do not actually contain a selenide ion, instead containing an iodoselenium cation. These cations include SeI3+, Se2I42+, Se6I22+, and polymeric Se6I+.
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It also decreases the function of tissue-resident macrophages, which are responsible for some bacterial clearance. Another toxin that inhibits the immune response is the adenylate cyclase toxin. This toxin has an intrinsic adenylate cyclase activity, increasing intracellular cAMP almost immediately. It is also able to form cation-specific pores in the membrane of the target cell.
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Neuroactive steroids bind to and modulate the activity of several ion channels including the GABAA, NMDA, and sigma receptors. The steroid progesterone has been found to modulate the activity of CatSper (cation channels of sperm) voltage-gated Ca2+ channels. Since eggs release progesterone, sperm may use progesterone as a homing signal to swim toward eggs (chemotaxis).
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This suggests that overexpression of ZIP family genes that encode cation transporters is a characteristic genetic feature of hyperaccumulation. Another gene family that has been observed ubiquitously in hyperaccumulators are the ZTP and ZNT families. A study on T. caerulescens identified the ZTP family as a plant specific family with high sequence similarity to other zinc transporter4.
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Sodium bifluoride is the inorganic compound with the formula NaHF2. It is a salt of sodium cation (Na+) and bifluoride anion (HF2−). It is a white, water- soluble solid that decomposes upon heating .Perry, Dale L.; Handbook of Inorganic Compounds; CRC Press (2011); page 381; Sodium bifluoride is non- flammable, hygroscopic, and has a pungent smell.
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Many sulfate esters are used in detergents, and some are useful reagents. Alkyl sulfates consist of a hydrophobic hydrocarbon chain, a polar sulfate group (containing an anion) and either a cation or amine to neutralize the sulfate group. Examples include: sodium lauryl sulfate (also known as sulfuric acid mono dodecyl ester sodium salt) and related potassium and ammonium salts.
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One application of lanthanum chloride is the removal of phosphate from solutions via precipitation, e.g. in swimming pools to prevent algae growth and other wastewater treatments. It has also shown use as a filter aid and an effective flocculent. Lanthanum chloride is also used in biochemical research to block the activity of divalent cation channels, mainly calcium channels.
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A thallium stress test is a form of scintigraphy in which the amount of thallium in tissues correlates with tissue blood supply. Viable cardiac cells have normal Na+/K+ ion-exchange pumps. The Tl+ cation binds the K+ pumps and is transported into the cells. Exercise or dipyridamole induces widening (vasodilation) of arteries in the body.
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The helium hydride ion HeH+ has been known since 1925. The protonated dihelium ion He2H+ can be formed when the dihelium cation reacts with dihydrogen: He + H2 → He2H+ \+ H. This is believed to be a linear molecule. Larger protonated helium cluster ions exist HenH+ with n from 3 to 14. He6H+ and He13H+ appear to be more common.
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Also CH3He+, OCHHe+ and NH2He+ have been detected. Young and Coggiola claimed to make HeC+ by an electric discharge off graphite into helium. When tritium substituted methane (CH3T) decays, CH3He+ is produced in a very small amount. The helium formyl cation, HeHCO+ is a linear molecule. It has a vibrational frequency red shifted 12.4 cm−1 compared to HCO+.
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A metal salen complex is a coordination compound between a metal cation and a ligand derived from N,N′-bis(salicylidene)ethylenediamine, commonly called salen. The classical example is salcomine, the complex with divalent cobalt , usually denoted as Co(salen). These complexes are widely investigated as catalysts and enzyme mimics. A square planar metal–salen complex.
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Although the exact biosynthesis of bipinnatin J has not been formally studied, the biosynthesis the core cembrane skeleton, neo-cembrene, has been extensively studied. Starting from geranylgeranyl pyrophosphate, the pyrophosphate leaves, creating the allyl carbocation. A type A cyclization then yields the 14-membered cembrane ring with the isopropyl cation outside the ring. Proton elimination then yields neo-cembrene.
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Strontiofluorite is a halide mineral that contains the alkali earth metal strontium and the halogen fluorine, a form of strontium fluoride. It can be considered a strontium-analogue of fluorite, which contains calcium as the dominant cation instead. It is translucent and pale gray in colour. It appears as cubo-octahedral crystals up to a size of 0.5 mm.
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Izatts thermodynamic results have been used in the development of macrocyclic and supramolecular chemistry,Izatt, R. et al Thermodynamic and kinetic data for cation-macrocycle interaction. Chem. Rev. 1985 vol 85 pp271-339.Izatt, R. et al Thermodynamic and kinetic data for macrocycle interaction with cations, anions and neutral molecules. Chem. Rev. 1995 vol 95 pp2529-2586.
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It would involve the unaided loss of the leaving group and the formation of an aryl cation. The nitro group is the most commonly encountered activating group, other groups are the cyano and the acyl group. The leaving group can be a halogen or a sulfide. With increasing electronegativity the reaction rate for nucleophilic attack increases.
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Counterions are the mobile ions in ion exchange polymers and colloids. Ion exchange resins are polymers with a net negative or positive charge. Cation exchange resins consist of an anionic polymer with countercations, typically Na+ (sodium). The resin has a higher affinity for highly charged countercations, for example by Ca2+ (calcium) in the case of water softening.
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The molecular orbital explanation of the stability of homoaromaticity has been widely discussed with numerous diverse theories, mostly focused on the homotropenylium cation as a reference. R.C. Haddon initially proposed a Mobius model where the outer electrons of the sp3 hybridized methylene bridge carbon(2) back-donate to the adjacent carbons to stabilize the C1-C3 distance.
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Norbornene undergoes an acid-catalyzed hydration reaction to form norborneol. This reaction was of great interest in the elucidation of the non-classical carbonion controversy. Norbornene is used in the Catellani reaction and in norbornene-mediated meta-C−H activation. Certain substituted norbornenes undergo unusual substitution reactions owing to the generation of the 2-norbornyl cation.
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When an insect ingests these proteins, they are activated by proteolytic cleavage. The N-terminus is cleaved in all of the proteins and a C-terminal extension is cleaved in some members. Once activated, the endotoxin binds to the gut epithelium and causes cell lysis by the formation of cation-selective channels, which leads to death.
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Carbenium ion of methane tert-Butyl cation, demonstrating planar geometry and sp2 hybridization Carbonium ion of methane A carbocation () is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountered (e.g., ethylene dication ).
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Fluocerite is a mineral, a cerium, lanthanum fluoride, formula . It is recognized as two different minerals depending on the cation, fluocerite-(Ce) and fluocerite-(La), corresponding respectively to lanthanum trifluoride and cerium trifluoride. Both crystallize in the trigonal system. Fluocerite-(Ce) was first described (without the Ce) in 1845 from hydrothermal veins in granite in Sweden.
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In line with the molecule's asymmetry, the charge is calculated as +0.10, +0.58 and +0.32 on each argon atom, so that it greatly resembles bound to a neutral Ar atom. Larger charged argon clusters are also detectable in mass spectroscopy. The tetraargon cation is also linear. icosahedral clusters have an core, whereas is dioctahedral with an core.
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TPCs have been implicated in fatty liver diseases, such as NAFLD and NASH. As TPC2 is a cation channel for endocytotic membrane trafficking, TPCs contribute in trafficking LDL molecules for their breakdown and recycling. This primarily occurs within the liver. The degradation pathway causes LDL to end up in endosomes and lysosomes – where TPCs are located.
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The structure of the aluminosilicate framework is the same for scolecite, natrolite and mesolite. Scolecite has long ordered chains, rotated 24° round the axis of the chain. One Ca cation and three H2O molecules are in four ion sites in the channels parallel to the c crystal axis. There is no sign of aluminium ions occupying silicon ion sites.
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William A. Albrecht (1888–1974)Springerlink, Obituary of William A. Albrecht, 1974 chairman of the Department of Soils at the University of Missouri, was the foremost authority on the relation of soil fertility to human health and earned four degrees from the University of Illinois at Urbana–Champaign. As emeritus professor of soils at the University of Missouri, he saw a direct link between soil quality, food quality and human health. He drew direct connections between poor quality forage crops, and ill health in livestock and from this developed a formula for ideal ratios of cations in the soil, the Base Cation Saturation Ratio. While he did not discover cation exchange in the soil as is sometimes supposed, he may have been the first to associate it with colloidal clay particles.
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The severe limitations on the arene component scope in this reaction is due primarily to the need for an arene radical anion that is stable enough not to react directly with enamine or enamine radical cation. In the proposed mechanism, the activated photoredox catalyst is quenched oxidatively by an electron-deficient arene, such as 1,4-dicyanobenzene. The photocatalyst then oxidizes an enamine species, transiently generated by the condensation of an aldehyde with a secondary amine cocatalyst, such as the optimal isopropyl benzylamine. The resulting enamine radical cation usually reacts as a 3 π-electron system, but due to the stability of the radical coupling partners, deprotonation of the β-methylene position gives rise to a 5 π-electron system with strong radical character at the newly accessed β-carbon.
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The liberated GAP deactivates activated-Transducin, terminating the phototransduction cascade (restoring dark current). # Low intracellular Ca2+ makes intracellular Ca- recoverin-RK dissociate into Ca2+ and recoverin and RK. The liberated RK then phosphorylates the Metarhodopsin II, reducing its binding affinity for transducin. Arrestin then completely deactivates the phosphorylated- metarhodopsin II, terminating the phototransduction cascade (restoring dark current). # Low intracellular Ca2+ make the Ca2+/Calmodulin complex within the cGMP-gated cation channels more sensitive to low cGMP levels (thereby, keeping the cGMP-gated cation channel open even at low cGMP levels, restoring dark current) In more detail: GTPase Accelerating Protein (GAP) interacts with the alpha subunit of transducin, and causes it to hydrolyse its bound GTP to GDP, and thus halts the action of phosphodiesterase, stopping the transformation of cGMP to GMP.
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The hydroxide ion is a natural part of water because of the self-ionization reaction in which its complement, hydronium, is passed hydrogen: :H3O+ \+ OH− 2H2O The equilibrium constant for this reaction, defined as :Kw = [H+][OH−][H+] denotes the concentration of hydrogen cations and [OH−] the concentration of hydroxide ions has a value close to 10−14 at 25 °C, so the concentration of hydroxide ions in pure water is close to 10−7 mol∙dm−3, in order to satisfy the equal charge constraint. The pH of a solution is equal to the decimal cologarithm of the hydrogen cation concentration;Strictly speaking pH is the cologarithm of the hydrogen cation activity the pH of pure water is close to 7 at ambient temperatures. The concentration of hydroxide ions can be expressed in terms of pOH, which is close to (14 − pH),pOH signifies the minus the logarithm to base 10 of [OH−], alternatively the logarithm of so the pOH of pure water is also close to 7. Addition of a base to water will reduce the hydrogen cation concentration and therefore increase the hydroxide ion concentration (increase pH, decrease pOH) even if the base does not itself contain hydroxide.
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The entry of imatinib into cells is dependent on an organic cation transporter (OCT1). OCT1 plays a significant role in imatinib resistance by inhibiting its influx and thus decreasing the intracellular bioavailability of imatinib. Patients with low expression, activity or polymorphisms of OCT1 had significantly lower intracellular levels of imatinib. The response of patients with low OCT1 activity was significantly dose-dependent.
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Perilymph is an extracellular fluid located within the inner ear. It is found within the scala tympani and scala vestibuli of the cochlea. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid. The major cation in perilymph is sodium, with the values of sodium and potassium concentration in the perilymph being 138 mM and 6.9 mM, respectively.
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Soil clay particles have varying effects on aggregate formation, depending on its type. Soil with 2:1 type of phyllosilicate clay minerals (e.g., montmoriollinite) typically have high cation exchange capacity (CEC), which allows them to bind with polyvalently charged organic matter complexes to form microaggregates (Amézketa, 1999). Soil organic matter is therefore the main binding agent in these soils (Six et al.
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Another shark fin like effect around 475 nm s due to X→D transitions. There is also a small hump with peaks at 601, 603 and 605.5 nm 1→3 triplet transitions and connected to the diffuse series. There are a few more small absorption features in the near infrared. There is also a dirubidium cation, Rb2+ with different spectroscopic properties.
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Since tyrosine kinase inhibitors (TKIs) are metabolized in the liver, interaction of TKIs with OATP1B1 and OATP1B3 can be considered as important molecular targets for transporter mediated drug-drug interactions. Along with the organic anion transporters, organic cation transporters and the ATP-binding cassette transporters, the OATPs play an important role in the absorption, distribution, metabolism and exretion (ADME) of many drugs.
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Due to a concentration gradient of the ions, mass transport must take place. As the larger cation diffuses from the molten salt into the surface, it replaces the smaller ion from the modifier. The larger ion squeezing into surface introduces compressive stress in the glass's surface. A common example is treatment of sodium oxide modified silicate glass in molten potassium chloride.
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They are closely associated with other minerals within the lakes, such as gypsum, halite, hematite, jarosite, and alunite. The stability of the minerals are predominately controlled by pH and cation availability, and where kaolinite is typically most stable at neutral pH's in others waters, the positive function of Al and Si ions to increasing acidity allow kaolinite to precipitate at pH extremes.
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As for oxide intercalation (or insertion) anode materials, similar classes of materials where the lithium cation is inserted into crystallographic vacancies within a metal host lattice have been discovered and studied since 1997. In general because of the metallic lattice, these types of materials, for example Cu6Sn5, Mn2Sb, lower voltages and higher capacities have been found when compared to their oxide counterparts.
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The ratio of four Ca to one Mg remains fairly steady, and no significant Ca/Mg substitution occurs in any cation site. Hence if the formula of picropharmacolite is written as Ca4Mg(H2O)7(AsO3OH)2(AsO4)2.4H2O,American MIneralogist (1981) 66:385 it is a better representation of the structure than the more usual formula Ca4Mg(AsO3OH)2(AsO4)2.11H2O.
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At the end is magnetite, while the composition is ulvöspinel. The titanomagnetites have an inverse spinel crystal structure and at high temperatures are a solid solution series. Crystals formed from titanomagnetites by cation-deficient oxidation are called titanomaghemites, an important example of which is maghemite. Another series, the titanohematites, have hematite and ilmenite as their end members, and so are also called hemoilmenites.
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The evaporation of a solution of in concentrated produces red crystals of gold(II) sulfate, Au2(SO4)2. Originally thought to be a mixed-valence compound, it has been shown to contain cations, analogous to the better-known mercury(I) ion, . A gold(II) complex, the tetraxenonogold(II) cation, which contains xenon as a ligand, occurs in [AuXe4](Sb2F11)2.
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Hyperpolarization is a change in a cell's membrane potential that makes it more negative. It is the opposite of a depolarization. It inhibits action potentials by increasing the stimulus required to move the membrane potential to the action potential threshold. Hyperpolarization is often caused by efflux of K+ (a cation) through K+ channels, or influx of Cl- (an anion) through Cl- channels.
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Tetramethylammonium (TMA) or (Me4N+) is the simplest quaternary ammonium cation, consisting of four methyl groups attached to a central nitrogen atom, and is isoelectronic with neopentane. It is positively charged and can only be isolated in association with a counter-ion. Common salts include tetramethylammonium chloride and tetramethylammonium hydroxide. Tetramethylammonium salts are used in chemical synthesis and are widely employed in pharmacological research.
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Laterite soils have a high clay content, which mean they have higher cation exchange capacity and water-holding capacity than sandy soils. It is because the particles are so small, the water is trapped between them. After rain, the water moves into the soil slowly. Palms are less likely to suffer from drought because the rain water is held in the soil.
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The protein encoded by this gene belongs to the family of P-type cation transport ATPases, and to the subfamily of aminophospholipid-transporting ATPases. The aminophospholipid translocases transport phosphatidylserine and phosphatidylethanolamine from one side of a bilayer to another. This gene is maternally expressed. It maps within the most common interval of deletion responsible for Angelman syndrome, also known as 'happy puppet syndrome'.
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Pigeonite is a mineral in the clinopyroxene subgroup of the pyroxene group. It has a general formula of (Ca,Mg,Fe)(Mg,Fe)Si2O6. The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations. Pigeonite crystallizes in the monoclinic system, as does augite, and a miscibility gap exists between the two minerals.
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Bioavailability, or the amount of a substance that is physiochemically accessible to microorganisms is a key factor in the efficient biodegradation of pollutants. O'Loughlin et al. (2000) showed that, with the exception of kaolinite clay, most soil clays and cation exchange resins attenuated biodegradation of 2-picoline by Arthrobacter sp. strain R1, as a result of adsorption of the substrate to the clays.
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The same year he was elected a specialty committee member of Higher Attestation Commission of the USSR. Further inventions of Genrikh Abaev were implemented in the procedures such as: butyl rubber synthesis technology process, paraffin C4-C5 two-stage dehydrogenation, isobutylene hydration process based on molded cation exchange resin. Abaev had received numerous awards and honours for his investigation of new manufacture technologies.
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Quadrupole moments of benzene and hexafluorobenzene. The polarity is inverted due to differences in electronegativity for hydrogen and fluorine relative to carbon; the inverted quadrupole moment of hexafluorobenzene is necessary for anion-pi interactions. In many respects, anion–π interaction is the opposite of cation–π interaction, although the underlying principles are identical. Significantly fewer examples are known to date.
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Sigma bond cleavage also occurs on radical cations remote from the site of ionization. This is commonly observed in alcohols, ethers, ketones, esters, amines, alkenes and aromatic compounds with a carbon attached to ring. The cation has a radical on a heteroatom or an unsaturated functional group. The driving force of fragmentation is the strong tendency of the radical ion for electron pairing.
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However, at low, sublytic concentrations, leukotoxin (TC# 1.C.11.1.1) causes activation of neutrophils, production of inflammatory cytokines, degranulation, generation of oxygen- derived free radicals, and morphologic changes consistent with apoptosis. The C-terminal domain of the adenylate cyclase toxin (ACT or CyaA; TC# 1.C.11.1.4) of Bordetella pertussis forms a small cation-selective channel, disrupting the permeability barrier.
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The crystal structure of magnesiopascoite consists of the decavanadate anion (V10O28)6− and interstitial {Ca2Mg(H2O)16}6+ consisting of Mg(H2O)6 octahedra and seven- fold coordinated CaO2(H2O)5. The structure differs from that of pascoite primarily in cation coordination in the interstitial complex. In addition to calcium and magnesium, magnesiopascoite contains minute quantities of zinc and cobalt.
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Ammonium bifluoride, as its name indicates, contains an ammonium cation (NH4+) and a bifluoride, or hydrogen(difluoride), anion (HF2−). The centrosymmetric triatomic bifluoride anion features the strongest known hydrogen bond, with a F−H length of 114 pm. and a bond energy greater than 155 kJ mol−1.Emsley, J. (1980) Very strong hydrogen bonds, Chemical Society Reviews, 9, 91–124.
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Diagram demonstrating the carbon cycle within peatlands. Mires have unusual chemistry, which influences inter alia their biota and the chemistry of the water outflow. Peat has very high cation-exchange capacity due to its high organic matter content: cations such as Ca2+ are preferentially adsorbed onto the peat in exchange for H+ ions. Water passing through peat declines in nutrients and in pH.
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However, even in this case, such solvated hydrogen cations are more realistically conceived as being organized into clusters that form species closer to H. Other oxonium ions are found when water is in acidic solution with other solvents. Although exotic on Earth, one of the most common ions in the universe is the ion, known as protonated molecular hydrogen or the trihydrogen cation.
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Perrhenate, like its conjugate acid perrhenic acid, features rhenium in the oxidation state of +7 with a d0 configuration. Solid perrhenate salts takes on the color of the cation. Typical perrhenate salts are the alkali metal derivatives and ammonium perrhenate. These salts are prepared by oxidation of rhenium compounds with nitric acid followed by neutralization of the resulting perrhenic acid.
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The condensation of formaldehyde, ammonia, and tris(ethylenediamine)cobalt(III) to give a clathrochelate complex is one example. 18-Crown-6 can be synthesized by the Williamson ether synthesis using potassium ion as the template cation. 2-aminobenzaldehyde. The phosphorus analogue of an aza crown can be prepared by a template reaction. where it is not possible to isolate the phosphine itself.
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Siloxides are chemical compounds with the formula R3SiOM, where R is usually an organic group and M is usually a metal cation. Also called silanoates, they are derived by deprotonation of silanols. They also arise by the degradation of siloxanes by base:Clemens Krempner "Role of Siloxides in Transition Metal Chemistry and Homogeneous Catalysis" Eur. J. Inorg. Chem. 2011, 1689–1698.
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Scandium nitride (ScN) is a binary III-V indirect bandgap semiconductor. It is composed of the scandium cation and the nitride anion. It forms crystals that can be grown on tungsten foil through sublimation and recondensation. It has a rock-salt crystal structure with lattice constant of 0.451 nanometer, a indirect bandgap of 0.9 eV and direct bandgap of 2 to 2.4 eV.
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The P2X4 subunits can form homomeric or heteromeric receptors. The P2X4 receptor has a typical P2X receptor structure. The zebrafish P2X4 receptor was the first purinergic receptor to be crystallized and have its three- dimensional structure solved, forming the model for the P2X receptor family. The P2X4 receptor is a ligand-gated cation channel that opens in response to ATP binding.
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Trifluoromethylisocyanide is the exception, its coordination properties are very similarly to those of CO. Because the CNC linkage is linear, the cone angle of these ligands is small, so it is easy to prepare polyisocyanide complexes. Many complexes of isocyanides show high coordination numbers, e.g. the eight-coordinate cation [Nb(CNBu-t)6I2]+. Very bulky isocyanide ligands are also known, e.g.
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Alpha-bisabolene synthase (, bisabolene synthase) is an enzyme with systematic name (2E,6E)-farnesyl-diphosphate diphosphate-lyase ((E)-alpha-bisabolene- forming). This enzyme catalyses the following chemical reaction : (2E,6E)-farnesyl diphosphate \rightleftharpoons (E)-alpha-bisabolene + diphosphate This synthase requires a divalent cation cofactor (Mg2+ or, to a lesser extent, Mn2+) to neutralize the negative charge of the diphosphate leaving group.
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Victoria blue BO, also known as C.I. Basic Blue 7 and C.I. 42595, is a chloride salt of a dye with the chemical formula [C33H40N3]Cl. It has the appearance of a reddish blue powder. Victoria Blue BO base, also known as Solvent Blue 5 and C.I. 42595:1, is the hydroxide derivative of the same cation. Its chemical formula is [C33H4oN3]OH.
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A family with recessive osteogenesis imperfecta has been reported to have a mutation in the TMEM38B gene on chromosome 9. This gene encodes TRIC-B, a component of TRIC, a monovalent cation-specific channel involved in calcium release from intracellular stores. It is extremely likely that there are other genes associated with this disease that have yet to be reported.
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Gallium maltolate is a coordination complex consisting of a trivalent gallium cation coordinated to three maltolate ligands. The compound is a potential therapeutic agent for cancer, infectious disease, and inflammatory disease. A cosmetic skin cream containing gallium maltolate is marketed under the name Gallixa. It is a colorless solid with significant solubility in both water and lipids (octanol-water partition coefficient = 0.41).
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Salts of hydrazinium are common reagents in chemistry and are often used in certain industrial processes.Jean-Pierre Schirmann, Paul Bourdauducq "Hydrazine" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2002. . Notable examples are hydrazinium hydrogensulfate, or , and hydrazinium azide, or . In the common names of such salts, the cation is often called "hydrazine", as in "hydrazine sulfate" for hydrazinium hydrogensulfate.
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It is a strongly cationic glycoprotein, and is purified with cation exchange resin. Purification of protein from bovine-derived stromal cell supernatants produces a substantially homogeneous factor, free of extraneous materials. The bovine protein is homologous with other mammalian species and is a homogeneous 50 kDa glycoprotein with an isoelectric point of 6.5. The protein is prepared in a lyophilized 1 microgram dose.
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The active site is formed by the center of the β subunit flanked by part of the α subunit. Farnesyltransferase coordinates a zinc cation on its β subunit at the lip of the active site. Farnesyltransferase has a hydrophobic binding pocket for farnesyl diphosphate, the lipid donor molecule. All farnesyltransferase substrates have a cysteine as their fourth-to-last residue.
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The first is an associative intermediate, where the R and X ligands bridge the two metals, stabilizing the transition state. The second and less common intermediate is the formation of a cation where R is bridging the two metals and X is anionic. The RTLE reaction proceeds in a concerted manner. Like in RT reactions, the reaction is driven by electronegativity values.
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Modification had also been extended past hydrophobic and hydrophilic attachments, charged compounds have also been introduced to TRPs. Kobayashi et al. had previously performed successful modifications to separate bioactive ionic compounds, and continued on that success to improve separation efficiency of bioactive compounds. Common methods of separating angiotensin peptides had involved reverse-phased high-performance liquid chromatography (RP-HPLC) and cation- exchange chromatography.
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Pannexins can form nonjunctional transmembrane “hemichannels” for transport of molecules of less than 1000 Da, or intercellular gap junctions. These hemichannels can be present in plasma, ER and Golgi membranes. They transport Ca2+, ATP, inositol triphosphate and other small molecules and can form hemichannels with greater ease than connexin subunits. Pannexin 1 constitutes the large conductance cation channel of cardiac myocytes.
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The McCormack reaction is a method for the synthesis of organophosphorus compounds. In this reaction a 1,3-diene and a source of R2P+ are combined to give phospholenium cation. The reaction is named after W. B. McCormack, a research chemist at duPont. An illustrative reaction involves phenyldichlorophosphine and isoprene: :320 px The reaction proceeds via a pericyclic [2+4]-process.
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The structure of ReO3 is similar to that of perovskite (ABO3), without the large A cation at the centre of the unit cell. Each rhenium center is surrounded by an octahedron defined by six oxygen centers. These octahedra share corners to form the 3-dimensional structure. The coordination number of O is 2, because each oxygen atom has 2 neighbouring Re atoms.
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Deprotonation gives the imidazole anion, which is symmetrical. As a base, the pKa of the conjugate acid (cited as pKBH+ to avoid confusion between the two) is approximately 7, making imidazole approximately sixty times more basic than pyridine. The basic site is the nitrogen with the lone pair (and not bound to hydrogen). Protonation gives the imidazolium cation, which is symmetrical.
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The miscibility of ionic liquids with water or organic solvents varies with side chain lengths on the cation and with choice of anion. They can be functionalized to act as acids, bases, or ligands, and are precursors salts in the preparation of stable carbenes. They have been found to hydrolyse. Because of their distinctive properties, ionic liquids have been investigated for many applications.
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Soil texture affects soil behaviour, in particular, its retention capacity for nutrients (e.g., cation exchange capacity) and water. Sand and silt are the products of physical and chemical weathering of the parent rock; clay, on the other hand, is most often the product of the precipitation of the dissolved parent rock as a secondary mineral, except when derived from the weathering of mica.
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Due to having octahedral symmetry, armalcolite has solid solution (cation substitution) between multiple elements Fe2+, Fe3+, Mg, Al, and Ti; this is because of their similarities in atomic radii and charge. The crystallographic structure exhibited by armalcolite is an orthombic- dipyramid, thus falls in the orthorhombic category and has a 2/m 2/m 2/m point group and space group of Bbmm.
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Oxatriquinacene is an organic cation with formula . It is an oxonium ion, with a trivalent oxygen atom with +1 charge connected to carbons 1,4, and 7 of a cyclononatriene ring, forming three fused pentagonal cycles. The compound may possess weak tris-homoaromatic character. Oxatriquinacene has remarkable stability compared to other oxonium cations, although not as extreme as that of the similar oxatriquinane.
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Silver perchlorate is noteworthy for its solubility in aromatic solvents such as benzene (52.8 g/L) and toluene (1010 g/L). In these solvents, the silver cation binds to the arene, as has been demonstrated by extensive crystallographic studies on crystals obtained from such solutions. Its solubility in water is extremely high, up to 500 g per 100 mL water.
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Tetraalkylammonium hydroxides, like alkali metal hydroxides, are very strong bases that react with atmospheric carbon dioxide to form carbonates. Furthermore, the nitrogen atom may be replaced by a phosphorus, arsenic, or antimony atom (the heavier nonmetallic pnictogens), creating a phosphonium () or arsonium () cation that can itself be substituted similarly; while stibonium () itself is not known, some of its organic derivatives are characterised.
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Along these lines, inhibitory postsynaptic potentials are useful in the signaling of the olfactory bulb to the olfactory cortex. EPSPs are amplified by persistent sodium ion conductance in external tufted cells. Low-voltage activated calcium ion conductance enhances even larger EPSPs. The hyperpolarization activated nonselective cation conductance decreases EPSP summation and duration and they also change inhibitory inputs into postsynaptic excitation.
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During the wood treatment process, the water-soluble copper and the quaternary ammonium cations are immobilized by the formation of stable insoluble compounds with lignin, cellulose, and hemicellulose and other wood components. The copper is the primary bactericide and fungicide agent. The quaternary ammonium cation is added to prevent growth of copper-tolerant bacteria, fungus, and mold, as an insecticide.
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The nonselective cation Transient Receptor Potential channel TRPM5 has been shown to correlate with both umami and sweet taste. Also, the phospholipase PLCβ2 was shown to similarly correlate with umami and sweet taste. This suggests that activation of the G-protein pathway and subsequent activation of PLC β2 and the TRPM5 channel in these taste cells functions to activate the cell.
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The nonselecive cation Transient Receptor Potential channel TRPM5 has been shown to correlate with both umami and sweet taste. Also, the phospholipase PLCβ2 was shown to similarly correlate with umami and sweet taste. This suggests that activation of the G-protein pathway and subsequent activation of PLC β2 and the TRPM5 channel in these taste cells functions to activate the cell.
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When the muscle generates force, the sensory terminals are compressed. This stretching deforms the terminals of the Ib afferent axon, opening stretch-sensitive cation channels. As a result, the Ib axon is depolarized and fires nerve impulses that are propagated to the spinal cord. The action potential frequency signals the force being developed by 10-20 extrafusal muscle fibers in the muscle.
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The coordination number of each atom in the structure is 8: the central cation is coordinated to 8 anions on the corners of a cube as shown, and similarly, the central anion is coordinated to 8 cations on the corners of a cube. Other compounds showing caesium chloride like structure are CsBr, CsI, high-temp RbCl, AlCo, AgZn, BeCu, MgCe, RuAl and SrTl.
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When standard acid catalysts such as sulfuric acid or a mix of BF3 and HF are used, the mechanismLi, J. J. In "Koch–Haaf carbonylation"; Name Reactions, 4th ed.; Springer, Berlin, 2009; p. 319. () begins by protonation of the alkene, followed by carbon monoxide attack of the resulting carbocation. The subsequent acylium cation is then hydrolysed to the tertiary carboxylic acid.
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21- and 18-membered diazacrown ether derivatives exhibit excellent calcium and magnesium selectivities and are widely used in ion-selective electrodes. Some or all of the oxygen atoms in crown ethers can be replaced by nitrogens to form cryptands. A well-known tetrazacrown is cyclen in which there are no oxygens. Lariat crown ethers have sidearms that can augment complexation of cation.
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Huheey, James E., Inorganic Chemistry (3rd ed., Harper & Row 1983), p.513–24 # Coordination isomerism – this occurs when both positive and negative ions of a salt are complex ions and the two isomers differ in the distribution of ligands between the cation and the anion. For example, [Co(NH3)6][Cr(CN)6] and [Cr(NH3)6][Co(CN)6].
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About 20 percent of dofetilide is metabolized in the liver via the CYP3A4 isoenzyme of the cytochrome P450 enzyme system. Drugs that interfere with the activity of the CYP3A4 isoenzyme can increase serum dofetilide levels. If the renal cation exchange system is interfered with (as with the medications listed above), a larger percentage of dofetilide is cleared via the CYP3A4 isoenzyme system.
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Metal aromaticity is believed to exist in certain clusters of aluminium, for example. Homoaromaticity is the state of systems where conjugation is interrupted by a single sp hybridized carbon atom. Y-aromaticity is used to describe a Y-shaped, planar (flat) molecule with resonance bonds. The concept was developed to explain the extraordinary stability and high basicity of the guanidinium cation.
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Styrene oxide is an epoxide derived from styrene. It can be prepared by epoxidation of styrene with peroxybenzoic acid, in the Prilezhaev reaction: 300px Styrene oxide is slightly soluble in water. A trace amount of acid in water causes hydrolysis to racemic phenylethyleneglycol via aryl cation. If the amount of water is not sufficient, acid-catalyzed isomerization for phenylacetaldehyde will occur.
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Recent rains remain variable. For instance, the rains in 2000 were not good, while those in 2001 were plentiful and well distributed. Soils that have become degraded, for example by intensive cereal production, cover 50 per cent of Niger's land. Laterite soils have a high clay content, which means they have higher Cation Exchange Capacity and water-holding capacity than sandy soils.
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Rubrene, like other polycyclic aromatic molecules, undergoes redox reactions in solution. It oxidizes and reduces reversibly at 0.95 V and −1.37 V, respectively vs SCE. When the cation and anion are co-generated in an electrochemical cell, they can combine with annihilation of their charges, but producing an excited rubrene molecule that emits at 540 nm. This phenomenon is called electrochemiluminescence.
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Urea contains a carbonyl group. The more electronegative oxygen atom pulls electrons away from the carbon forming a greater electron density around the oxygen, giving the oxygen a partial negative charge and forming a polar bond. When nitric acid is presented, it ionizes. A hydrogen cation contributed by the acid is attracted to the oxygen and forms a covalent bond [electrophile H+].
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In molecular clouds, simple carbon molecules are formed, including carbon monoxide and dicarbon. Reactions with the trihydrogen cation of the simple carbon molecules yield carbon containing ions that readily react to form larger organic molecules. Carbon compounds that exist as ions, or isolated gas molecules in the interstellar medium, can condense onto dust grains. Carbonaceous dust grains consist mostly of carbon.
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The enthalpy of formation ΔfH0 of tetra-n-butylammonium iodide is −499 kJ/mol, which is lower than that for the bromide or chloride (−540, −564 kJ/mol). At lower temperatures with water tetra-n-butylammonium iodide forms a clathrate hydrate. The tetra-n-butylammonium cation is large and hydrophobic. The absolute enthalpy of hydration (from gas phase) is −260 kJ/mol.
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Bulk potassium alum . An alum () is a type of chemical compound, usually a hydrated double sulfate salt of aluminium with the general formula , where X is a monovalent cation such as potassium or ammonium. By itself, "alum" often refers to potassium alum, with the formula . Other alums are named after the monovalent ion, such as sodium alum and ammonium alum.
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Jeremy Barnes (born 18 September 1976) is an American musician. He plays accordion, percussion and other instruments. He has been a member of the bands Neutral Milk Hotel, Beirut, and A Hawk and a Hacksaw, and is a co-creator of the record label L.M. Dupli-cation. Influences on his work include music from Eastern Europe, Turkey, and the Caucasus.
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Other conditions for iodination include I2, HIO3, H2SO4, and N-iodosuccinimide, H2SO4. These conditions are successful for highly deactivated arenes, including nitroaromatics. In a series of studies, the powerful reagent obtained by using a mixture of iodine and potassium iodate dissolved in concentrated sulfuric acid was used. Here the iodinating agent is the triiodine cation I3+ and the base is HSO4−.
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Editing results in a codon change from a glutamine codon (CAG) to an arginine codon (CIG). Editing at R/G results in a codon change. The region of the editing site is known to be the region that controls divalent cation permeability. The other ionotropic AMPA glutamate receptors have a genomically encoded have a glutamine residue, while GluR2 has an arginine.
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Californium(III) bromide Few compounds of californium have been made and studied. The only californium ion that is stable in aqueous solutions is the californium(III) cation. The other two oxidation states are IV (strong oxidizing agents) and II (strong reducing agents). The element forms a water- soluble chloride, nitrate, perchlorate, and sulfate and is precipitated as a fluoride, oxalate or hydroxide.
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Lippincott, Williams & Wilkins These activated protein kinases serve to phosphorylate post-synaptic excitatory receptors (e.g. AMPA receptors), improving cation conduction, and thereby potentiating the synapse. Also, these signals recruit additional receptors into the post-synaptic membrane, stimulating the production of a modified receptor type, thereby facilitating an influx of calcium. This in turn increases post-synaptic excitation by a given pre-synaptic stimulus.
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He was predicted to exist by Linus Pauling in 1933. It was discovered when doing mass spectroscopy on ionised helium. The dihelium cation is formed by an ionised helium atom combining with a helium atom: He+ \+ He → He. The diionised dihelium He (1Σ) is in a singlet state. It breaks up He → He+ \+ He+ releasing 200 kcal/mol of energy.
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Malachite green is classified in the dyestuff industry as a triarylmethane dye and also using in pigment industry. Formally, malachite green refers to the chloride salt [C6H5C(C6H4N(CH3)2)2]Cl, although the term malachite green is used loosely and often just refers to the colored cation. The oxalate salt is also marketed. The anions have no effect on the color.
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Although similar methods were applied in Asia as in Europe, the steady state mass balance approach has been improved by considering base cation deposition. Steady-state mass balance critical loads have been used to designate Acid Rain Control Zones and Sulphur Dioxide Pollution Control Zones in China. In the near future, critical loads will be more widely applied to guide emission abatement strategies.
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Ferric oxide, commonly, though not precisely, called rust. In chemistry, iron(III) refers to the element iron in its +3 oxidation state. In ionic compounds (salts), such an atom may occur as a separate cation (positive ion) denoted by Fe3+. The adjective ferric or the prefix ferri- is often used to specify such compounds — as in "ferric chloride" for iron(III) chloride, .
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It is then treated with high-pressure elution from cation exchange resins, and the berkelium phase is oxidized and extracted using one of the procedures described above. Reduction of the thus- obtained to the +3 oxidation state yields a solution, which is nearly free from other actinides (but contains cerium). Berkelium and cerium are then separated with another round of ion-exchange treatment.
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Although dibromine is a strong oxidising agent with a high first ionisation energy, very strong oxidisers such as peroxydisulfuryl fluoride (S2O6F2) can oxidise it to form the cherry-red cation. A few other bromine cations are known, namely the brown and dark brown .Greenwood and Earnshaw, pp. 842–4 The tribromide anion, , has also been characterised; it is analogous to triiodide.
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Finally, the C1 atom of UDP-glucose undergoes nucleophilic attack by an oxygen atom in fructose 6-phosphate, resulting in glucosyl group transfer to fructose 6-phosphate. Whether or not this mechanism requires a divalent ion is currently unclear, but failed attempts to trap and detect the presence of the magnesium cation suggest that this mechanism is metal ion independent.
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Silver hyponitrite is sparingly soluble in concentrated alkali hyponitrite solutions, but quite soluble in aqueous ammonia due to the formation of the complex cation [()2Ag]+.C.N. Polydoropoulos, Th. Yannakopoulos (1961), "Silver hyponitrite: Solubility product and complexes in aqueous ammonia". Journal of Inorganic and Nuclear Chemistry, volume 19, issues 1–2, pages 107–114. The compound is slowly decomposed by light.
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Trimethylamine (TMA) is an organic compound with the formula N(CH3)3. It is a colorless, hygroscopic, and flammable tertiary amine. It is a gas at room temperature but is usually sold as a 40% solution in water. (It is also sold in pressurized gas cylinders.) TMA is a nitrogenous base and can be readily protonated to give trimethylammonium cation.
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This gene encodes a member of the cyclic nucleotide-gated cation channel protein family, which is required for normal vision and olfactory signal transduction. CNGA3 is expressed in cone photoreceptors and is necessary for color vision. Missense mutations in this gene are associated with rod monochromacy and segregate in an autosomal recessive pattern. Two alternatively-spliced transcripts encoding different isoforms have been described.
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Organic cation transporter 3 is a polyspecific transporter whose transport is independent of sodium. Known substrates for transport include: histamine, serotonin, norepinephrine, dopamine and MPP+. Capacity for transport and affinity for these substrates may vary between rat and human isoforms however. Transport activity of OCT3 is inhibited by recreational and pharmaceutical drugs, including MDMA, phencyclidine (PCP), MK-801, amphetamine, methamphetamine and cocaine.
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Izatt and his colleagues were the first to attach macrocycles to a solid matrix and make highly selective metal separations.Izatt, R. et al Removal and separation of metal ions from aqueous solutions using a silica gel bonded macrocycle system. Anal. Chem. 1988 vol 60 pp1825-1826.Bradshaw, J. et al Preparation of silica gel bound macrocycles and their cation binding properties.
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The hexahydrate consists of octahedral [Al(H2O)6]3+ centers and chloride counterions. Hydrogen bonds link the cation and anions. The hydrated form of aluminium chloride has an octahedral molecular geometry, with the central aluminum ion surrounded by six water ligand molecules. Being coordinatively saturated, the hydrate is of little value as a catalyst in Friedel-Crafts alkylation and related reactions.
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Studying these cations was sparked, at the time, by amazing results in computational chemistry. While calculating the optimal geometry of the mono- cation which arises from the extraction of chloride from 3-chlorotricyclo[2.1.0.02,5]pentane, the three bridges were expected to orient in space with angles of roughly 120°. The calculations however showed the four-sided pyramid to be the most stable configuration.
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The popularization of NHC ligands can be traced to Arduengo, who reported the deprotonation of dimesitylimidazolium cation to give IMes. IMes is a free NHC that can be used as a ligand. Other NHCs have been isolated as the free ligands. Aside from IMes, another important NHC ligand is IPr, which features diisopropylphenyl groups in place of the mesityl groups.
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The argon dihydrogen cation has been predicted to exist and to be detectable in the interstellar medium. However it has not been detected . is predicted to be linear in the form Ar−H−H. The H−H distance is 0.94 Å. The dissociation barrier is only 2 kcal/mol (8 kJ/mol), and readily loses a hydrogen atom to yield ArH+.
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Despite the wide range of organisms that synthesize protoporphyrin IX the process is largely conserved from bacteria to mammals with a few distinct exceptions in higher plants. In the biosynthesis of those molecules, the metal cation is inserted into protoporphyrin IX by enzymes called chelatases. For example, ferrochelatase converts the compound into heme b (i.e. Fe-protoporphyrin IX or protoheme IX).
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The sensitivity of this method relies on the high mobility of H+ in comparison with the mobility of other cations or anions. Beyond cation conductivity, there are analytical instruments designed to measure Degas conductivity, where conductivity is measured after dissolved carbon dioxide has been removed from the sample, either through reboiling or dynamic degassing. Conductivity detectors are commonly used with ion chromatography.
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Incidence among wether lambs can be minimized by maintaining a dietary Ca:P intake ratio of 2:1. Alkaline (higher) pH favors formation of carbonate and phosphate calculi. For domestic ruminants, dietary cation: anion balance is sometimes adjusted to assure a slightly acidic urine pH, for prevention of calculus formation. Differing generalizations regarding effects of pH on formation of silicate uroliths may be found.
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The urine test strip test for specific gravity is based on the change in dissociation constant (pKa) of an anionic polyelectrolyte (poly-(methyl vinyl ether/maleic anhydride)) in an alkali medium that is ionised and releases hydrogen ions in proportion to the number of cations present in the solution. The greater the cation concentration of the urine the more hydrogen ions are released, thereby reducing the pH. The pad also includes bromothymol blue, which measures this change in pH. It should be remembered that the test strip only measures cation concentration, it is therefore possible that urine with a high concentration of non-ionic solutes (such as glucose or urea) or with high molecular weight compounds (such as the media used to provide radiographic contrast) will yield a result that will be erroneously lower than that measured by densitometry.
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The bond valence model can be reduced to the traditional ionic model if certain conditions are satisfied. These conditions require that atoms be divided into cations and anions in such a way that (a) the electronegativity of every anion is equal to, or greater than, the electronegativity of any of the cations, (b) that the structure is electroneutral when the ions carry charges equal to their valence, and (c) that all the bonds have a cation at one end and an anion at the other. If these conditions are satisfied, as they are in many ionic and covalent compounds, the electrons forming a bond can all be formally assigned to the anion. The anion thus acquires a formal negative charge and the cation a formal positive charge, which is the picture on which the ionic model is based.
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Frost's proteges were drafted the following season by Ontario Hockey League (OHL) teams; he was known to frequently attend Sarnia Sting games to monitor the progress of Jefferson, who would eventually be dealt to the Toronto St. Michael's Majors to play with Sheldon Keefe, Ryan Barnes and Shawn Cation, who rounded out the rest of Frost's "Brampton Boys". Frost, not officially associated with the team, created so many conflicts with the St. Mike's front office that all four of his "Brampton Boys" were traded to the Barrie Colts. The Brampton Boys tenure in Barrie, while productive on the ice, was accompanied by bizarre behavior, especially compared to the traditional deference shown by junior players. Ryan Barnes was suspended for 25 games for a stick-swinging incident, while Shawn Cation was suspended for 15 games for instigating a line brawl.
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The magnetic properties of the β-CrPO4 are a result of the cation-cation distances along the octahedral chains which give rise to strong direct-exchange interactions and even metal- metal bonding. Neutron diffraction studies reveal that the spiral moments in β-CrPO4 are collinear and anti-ferromagnetically coupled along the chains in the 001 planes, at low temperature (5K, µeff = 2.55µB). Observations from a diffraction study has shown that at low temperature(2K), the α-CrPO4 octahedra CrO6 units build up an infinite, three-dimensional network expected to provide strong Cr-O-Cr magnetic superexchange linkages with exchange pathway through the phosphate group. These linkages give the structure its anti-ferromagnetic characteristic (Ɵ = -35.1 K, µeff = 3.50µB) which results in the anti-parallel magnetic spins in the plane that is perpendicular to the chains of the octahedral CrO6.
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Harpoon reactionsIUPAC Goldbook definition of harpoon reaction are a type of chemical reaction between two substances: one (generally a metal) prone to form a cation, and the other (generally a halogen) prone to form an anion. Their main feature is that these reactions, unlike most reactions, have steric factors greater than unity, that is, they take place faster than predicted by collision theory. This is explained by the fact that the colliding particles have greater cross sections than the pure geometrical ones calculated from their radii, because when the particles are close enough, an electron "jumps" (therefore the name) from one of the particles to the other one, forming an anion and a cation which subsequently attract each other. Harpoon reactions usually take place in the gas phase, but they are also possible in condensed media.
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Houghton Mifflin, 2007, Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic. In summary, this can be represented as the following chemical reaction: :Acid + Base Conjugate Base + Conjugate Acid Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge; it is represented by the symbol H+ because it constitutes the nucleus of a hydrogen atom, that is, a hydrogen cation. A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint.
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A Hawk and a Hacksaw is an American folk duo from Albuquerque, New Mexico, currently signed to L.M. Dupli-cation. The band consists of accordionist Jeremy Barnes, who was previously the drummer for Neutral Milk Hotel and Bablicon, and violinist Heather Trost. The music is inspired by Eastern European, Turkish and Balkan traditions, and is mostly instrumental. They have released six albums and have toured internationally.
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The displacement of those protons and insertion of a metal cation requires the presence of chelatases. Chelatases are required because porphyrins and related macrocyclic ligands are extremely slow to metalate, despite favorable thermodynamics. These low rates are attributed to the tight fit of the metal into the rigid 18- or 17-membered tetrapyrrole macrocycle. Several families of chelatase are known including cobalt chelatase, magnesium chelatase, and ferrochelatase.
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For strong electrolytes, a single reaction arrow shows that the reaction occurs completely in one direction, in contrast to the dissociation of weak electrolytes, which both ionize and re-bond in significant quantities.Brown, Theodore L. Chemistry: The Central Science, 9th edition. :Strong electrolyte(aq) -> Cation+(aq) + Anion−(aq) Strong electrolytes conduct electricity only when molten or in aqueous solutions. Strong electrolytes break apart into ions completely.
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The helium hydride ion or hydridohelium(1+) ion or helonium is a cation (positively charged ion) with chemical formula HeH+. It consists of a helium atom bonded to a hydrogen atom, with one electron removed. It can also be viewed as protonated helium. It is the lightest heteronuclear ion, and is believed to be the first compound formed in the Universe after the Big Bang.
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Formation of ammonium Ammonium cation is found in a variety of salts such as ammonium carbonate, ammonium chloride and ammonium nitrate. Most simple ammonium salts are very soluble in water. An exception is ammonium hexachloroplatinate, the formation of which was once used as a test for ammonium. The ammonium salts of nitrate and especially perchlorate are highly explosive, in these cases ammonium is the reducing agent.
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N-Fluoropyridinium triflate is an organofluorine compound with the formula [C5H5NF]O3SCF3, It is a white solid with low solubility in polar organic solvents. The compound is used as an electrophilic fluorinating agent. It is a salt, consisting of the N-fluoropyridinium cation ([C5H5NF]+) and the triflate anion. Teruo Umemoto, Ahmad El-Awa "N-Fluoropyridinium Triflate" e-EROS Encyclopedia of Reagents for Organic Synthesis.
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In soil solution, various plant nutrients derived from minerals and organic matters in the soil are there. This is measured through the cation exchange capacity. Large pores serve as water drainage pipe to allow the excessive water pass through the soil, during the heavy rains. They also serve as air tank to supply oxygen to plant roots and other living beings in the soil.
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Myricetin was shown to create reactive oxygen species that caused the DNA damage. It has been demonstrated that myricetin, depending on its concentration, displays different oxidizing effects on DNA. Polyphenols like myricetin are able to reduce (donate electrons to) Fe3+. Thus, this reaction yields a less oxidized (more reduced) form of the iron cation: Fe2+ and a less reduced (more oxidized) form of myricetin.
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RhTx binds to the outer pore region of the polymodal TRPV1 ion channel. The toxin preferably binds to TRPV1 in the activated state of the channel. RhTx has a high affinity for the TRPV1 ion channel, which results in very rapid binding and slow unbinding. The TRPV1 channel is a non-selective cation channel, with a high permeability to Ca2+.Caterina, M. J., & Julius, D. (2001).
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The mineral crystallises in the monoclinic crystal system. Most sources put it in the prismatic class 2/m, with space group P21/m, but Webmin puts it in the sphenoidal class 2 with space group P21. The structure is similar to that of dolomite, but with two crystallographically different CO3 groups. The cation layers are stacked in an ABCABC... stacking pattern, repeating every 3 layers.
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A.6) and elicits a hypersensitive response (HR) in non-host plants upon infection and pathogenicity in hosts. It contains several repetitive regions and exhibits two extended (20 residue) regions of moderate hydrophobicity that might serve as α-helical TMSs. The HrpZ cation channel is predicted to be largely of α-structure. HrpZ - a harpin - is a highly thermostable protein that exhibits multifunctional abilities, e.g.
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In order to generate bilobalide, C20 ginkgolide 13 must form first. To transform from GGPP to abietenyl cation 5, a single bifunctional enzyme abietadiene synthase E1 is required. However, due to the complexity of ginkgolide structures for rearrangement, ring cleavage, and formation of lactone rings, diterpene 8 is used to explain instead. Levopimaradiene 6 and abietatriene 7 are precursors for ginkgolide and bilobalide formation.
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Diadenosine hexaphosphate hydrolase (AMP-forming) (, hAps1, NUDT11 (gene), hAps2, NUDT10 (gene)) is an enzyme with systematic name P1,P6-bis(5'-adenosyl)hexaphosphate nucleotidohydrolase (AMP-forming). This enzyme catalyses the following chemical reaction : (1) P1,P6-bis(5'-adenosyl)hexaphosphate + H2O \rightleftharpoons adenosine 5'-pentaphosphate + AMP : (2) P1,P5-bis(5'-adenosyl)pentaphosphate + H2O \rightleftharpoons adenosine 5'-tetraphosphate + AMP A divalent cation is essential for activity.
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Antitranspirants are compounds applied to the leaves of plants to reduce transpiration. They are used from Christmas trees, on cut flowers, on newly transplanted shrubs, and in other applications to preserve and protect plants from drying out too quickly. They have also been used to protect leaves from salt burn and fungal diseases . They block the active excretion of hydrogen cation from the guard cells.
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Nucleophilic alkylating agents deliver the equivalent of an alkyl anion (carbanion). The formal "alkyl anion" attacks an electrophile, forming a new covalent bond between the alkyl group and the electrophile. The counterion, which is a cation such as lithium, can be removed and washed away in the work-up. Examples include the use of organometallic compounds such as Grignard (organomagnesium), organolithium, organocopper, and organosodium reagents.
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The protein encoded by this gene is a non-selective calcium-permeable cation channel and is part of the Transient Receptor Potential ion channel super family. The closest relative is the cold and menthol activated TRPM8 ion channel. While TRPM2 is not cold sensitive it is activated by heat. The TRPM2 ion channel is activated by free intracellular ADP-ribose in synergy with free intracellular calcium.
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PPN+ forms crystalline salts with a range of anions that are otherwise difficult to crystallize. Its effectiveness is partially attributable to its rigidity, reflecting the presence of six phenyl rings. Often PPN+ forms salts that are more air-stable than salts with smaller cations such as those containing quaternary ammonium or alkali metal cations. This effect is attributed to the steric shielding provided by this voluminous cation.
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