39 Sentences With "selectivities" | Random Sentence Generator

400x400px Together, these advantages provide Co(II)–porphyrin catalysts with high catalytic selectivities and turnover numbers.

Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities.

The selectivities of these channels may be relatively weak in comparison to voltage-gated channels. In addition, some MscS channels may function in amino acid efflux, Ca2+ regulation and cell division.

This property is referred to as the "intrinsic safety" of microstructured reactors. The improvement of yields and selectivities by using novel reactions or running reactions at more extreme parameters is known as "process intensification".

Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities. Alternative splice variants of GRM8 have been described but their full-length nature has not been determined.

Many useful Lewis acid-catalyzed ene reactions have been also developed, which can afford high yields and selectivities at significantly lower temperatures, making the ene reaction a useful C–C forming tool for the synthesis of complex molecules and natural products.

They are located on different body regions depending on the animal, such as on the tail for crayfish and lobsters.Douglass, J K, and L A Wilkens. “Directional selectivities of near-field filiform hair mechanoreceptors on the crayfish tailfan (Crustacea: Decapoda).” Journal of Comparative Physiology A 183 (1998): 23-34.

W. Partenheimer and V.V. Grushin, Adv. Synth. Catal., 2001, 343, 102–111. Also, the direct, one pot dehydration and oxidation of fructose to FDCA via intermediate HMF has been investigated with good selectivities, unfortunately this system does not work in water.C. Carlini, P. Patrono, A.M.R. Galletti, G. Sbrana and V. Zima, Appl. Catal.

Simmons-Smith cyclopropanation, which employs carbenes derived from diethylzinc and diiodomethane, is a popular alternative to rhodium-catalyzed cyclopropanation. In the presence of a chiral diamine, Simmons-Smith cyclopropanation is enantioselective; however, selectivities are not as high as the corresponding rhodium-catalyzed reactions.Denmark, S. E.; O'Connor, S. P. J. Org. Chem. 1997, 62, 3390. (13)File:IntraCPAlt1.

Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities. Alternative splice variants of the GRM1 gene have been described but their full-length nature has not been determined. A possible connection has been suggested between mGluRs and neuromodulators, as mGluR1 antagonists block adrenergic receptor activation in neurons.

Oxidation catalysis is conducted by both heterogeneous catalysis and homogeneous catalysis. In the heterogeneous processes, gaseous substrate and oxygen (or air) are passed over solid catalysts. Typical catalysts are platinum, and redox-active oxides of iron, vanadium, and molybdenum. In many cases, catalysts are modified with a host of additives or promoters that enhance rates or selectivities.

The two most common problems in this class of reactions are low ortho/para selectivities and dearomatization (the latter is a particularly significant problem for phenols).Zupan, M.; Iskra, J.; Stavber, S. Bull. Chem. Soc. Jpn. 1995, 68, 1655. :File:EFScope5.png Enol ethers and glycals are nucleophilic enough to be fluorinated by Selectfluor.Albert, M.; Dax, K.; Ortner, J. Tetrahedron 1998, 54, 4839.

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.

Styrene can be produced from toluene and methanol, which are cheaper raw materials than those in the conventional process. This process has suffered from low selectivity associated with the competing decomposition of methanol. Exelus Inc. claims to have developed this process with commercially viable selectivities, at 400–425 °C and atmospheric pressure, by forcing these components through a proprietary zeolitic catalyst.

For instance, cyclohexane has been converted to cyclohexanone and cyclohexanol with a combined selectivity of ~100% on gold catalysts. Product selectivities can be tuned in liquid phase reactions by the presence or absence of solvent and by the nature of the latter, viz. water, polar, or nonpolar. With gold catalysts, the catalyst's support has less influence on reactions in the liquid phase than on reactions in the gas phase.

Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities. Alternative splice variants of GRM8 have been described but their full-length nature has not been determined. Emerging research strongly points to mGluR5 playing a direct role in the pathogenesis of alcohol use disorder in humans, showing intimate involvement in the development of behavioral sensitization towards ethanol in animal models.

NBS will react with alkenes 1 in aqueous solvents to give bromohydrins 2. The preferred conditions are the portionwise addition of NBS to a solution of the alkene in 50% aqueous DMSO, DME, THF, or tert-butanol at 0 °C. Formation of a bromonium ion and immediate attack by water gives strong Markovnikov addition and anti stereochemical selectivities. :Bromohydrin formation Side reactions include the formation of α-bromoketones and dibromo compounds.

Dynorphins exert their effects primarily through the κ-opioid receptor (KOR), a G-protein-coupled receptor. Two subtypes of KORs have been identified: K1 and K2. Although KOR is the primary receptor for all dynorphins, the peptides do have some affinity for the μ-opioid receptor (MOR), δ-opioid receptor (DOR), and the N-methyl-D- aspartic acid (NMDA)-type glutamate receptor. Different dynorphins show different receptor selectivities and potencies at receptors.

Drugs that act on the opioid system generally vary in selectivity for the mu (μ), delta (δ), and kappa (κ) opioid receptors. Their addictive properties are highly dependent on these selectivities. Generally speaking, high potency mu- opioid receptor (MOR) agonists have high abuse potential, while kappa-opioid receptor (KOR) agonists generally produce a dysphoric state. Morphine, a MOR agonist, was one of the earliest studied drugs at the advent of ICSS and BSR.

In humans ENT are also known as SLC29, a group of plasmalemmal transport proteins which transport nucleoside substrates like adenosine into cells. There are four known human ENTs, designated ENT1, ENT2, ENT3, and ENT4. They are blocked by adenosine reuptake inhibitors like dipyridamole and dilazep, drugs used clinically for their vasodilatory properties. The best- characterized members of the human Ent family, hENT1 and hENT2, possess similar broad permeant selectivities for purine and pyrimidine nucleosides, but hENT2 also efficiently transports nucleobases.

Zeolites, a class of porous aluminosilicate solids, are currently used in a wide variety of industrial and commercial applications including CO2 separation. The capacities and selectivities of many zeolites are among the highest for adsorbents that rely upon physisorption. For example, zeolite Ca-A (5A) has been reported to display both a high capacity and selectivity for CO2 over N2 under conditions relevant for carbon capture from coal flue gas, although it has not been tested in the presence of H2O.Bae, T.-H.

Additionally targets have been rationally identified by using a powerful seqecune-based design approach termed informal to identify dozens of bioactive small molecules that target disease causing non-coding RNA termed INFORNA. This study important showed for the first time that small molecules appear to have selectivities that are competitive with oligonucleotides with cell-permeable and medicinally optimizable small molecules. Additionally, compounds have been shown to be bioactive in diverse disease settings that ranged from breast cancer. and hepatocellular carcinoma.

The electrophilic addition reaction of hydrogen bromide to 1,3-butadiene above room temperature leads predominantly to the thermodynamically more stable 1,4 adduct, 1-bromo-2-butene, but decreasing the reaction temperature to below room temperature favours the kinetic 1,2 adduct, 3-bromo-1-butene. The addition of HBr to butadiene in ether. Data from Elsheimer (2000). :The rationale for the differing selectivities is as follows: Both products result from Markovnikov protonation at position 1, resulting in a resonance-stabilized allylic cation.

Borane dimethylsulfide is one of the most common bulk reducing agents used in the Corey–Itsuno reduction. The dimethylsulfide ligand attenuates the reactivity of the borane. Activation by the nitrogen of the chiral oxazoborolidine catalyst of the stoichiometric reducing agent allows for asymmetric control of the reagent. In general BMS does not lead to significantly greater enantiomeric selectivities than borane-THF, however its increased stability in the presence of moisture and oxygen makes it the reagent of choice for the reduction.

Although the epoxidation of ethylene is routinely achieved in the industry with selectivities as high as 90% on Ag catalysts, most catalysts provided < 10% selectivity for propylene epoxidation. Using a gold catalyst supported on titanium silicate-1 (TS-1) molecular sieve, yields of 350 g/h per gram of gold were obtained at 473 K (200 °C). The reaction took place in the gas phase. Furthermore, using mesoporous titanosilicate supports (Ti-MCM-41 and Ti-MCM-48), gold catalysts provided > 90% selectivity at ~ 7% propylene conversion, 40% H2 efficiency, and 433 K (160 °C).

The active species in these catalysts were identified to be hemispherical gold nano-crystals of less than 2 nm in diameter in intimate contact with the support. Alkene epoxidation has been demonstrated in absence of H2 reuductant in the liquid phase. For example, using 1% Au/graphite, ~80% selectivities of cis-cyclooctene to cyclooctene oxide (analogous to cyclohexene oxide) were obtained at 7-8% conversion, 353 K (80 °C), and 3 MPa O2 in absence of hydrogen or solvent. Other liquid-phase selective oxidations have been achieved with saturated hydrocarbons.

Group II and III receptors are linked to the inhibition of the cyclic AMP cascade but differ in their agonist selectivities. mGluR6 is specifically expressed in the retina, in a subtype of bipolar cells that depolarize in response to light, known as ON bipolar cells. These cells form synapses with photoreceptor cells, and detect the neurotransmitter glutamate via a GPCR signal transduction cascade. The glutamate receptor mGluR6 is located post-synaptically at the tips of the bipolar cell dendrites, and is responsible for initiating a signaling cascade that ultimately controls gating of the TRPM1 channel.

This phenomenon is demonstrated by observed selectivities in the rearrangements below. In the rearrangement on the left the thermodynamically unfavorable product is observed exclusively, while in the reaction on the right the product derived from the less stable radical intermediate is favored. Evidence for selectivity based on nitrogen lone pair orientation. Aubé takes advantage of this rearrangement as the key step in his synthesis of (+)-yohimbine, a natural medicine classified by the NIH as possibly effective in the treatment of erectile dysfunction and the sexual problems caused by selective serotonin reuptake inhibitors.

Since almost all adsorptive separation processes are dynamic -meaning, that they are running under flow - testing porous materials for those applications for their separation performance has to be tested under flow as well. Since separation processes run with mixtures of different components, measuring several breakthrough curves results in thermodynamic mixture equilibria - mixture sorption isotherms, that are hardly accessible with static manometric sorption characterization. This enables the determination of sorption selectivities in gaseous and liquid phase. The determination of breakthrough curves is the foundation of many other processes, like the pressure swing adsorption.

The direct selection for biological traits through fishery practices is the result of fishery management regulations, and gear restrictions and selectivities. The most obvious artificial selection for traits through management legislation can be observed in the imposed regulations on size, sex, seasonality, and locations. Catch size regulations vary with specificity to the targeted species and is often used to prevent exploitation during a specific part of the life cycle for the organism. Such regulations arose in response to the effects of FIE observed by the fisheries of Atlantic Cod (Gadus morhua).

Professor Dordick currently leads the Jonathan S. Dordick Research Group, which works in part at the Center for Biotechnology and Interdisciplinary Studies working on biomedical technologies.The Jonathan S. Dordick Research Group Present and past research has included studies of Biocatalysis in Nonaqueous Media, Combinatorial Biocatalysis, Nanobiotechnology, enzyme technology, molecular bioprocessing. More specifically, they work on the development of enzymatic catalysis under extreme conditions (e.g. high salt concentrations), enzymes in the synthesis and modification of polymeric materials, combinatorial biocatalysis for drug discovery and polymer synthesis, and the generation of biocatalysts and biomimetics with unique activities and selectivities.

The mixed agonists-antagonists drug class exerts their analgesic actions by agonistic activity at the KOR. While all drugs in this class possess MOR antagonistic activity leading to less abuse potential, nalbuphine is the only approved drug in the mixed agonist-antagonist class listed in terms of its pharmacological actions and selectivities on opioid receptors as a MOR partial agonist or antagonist as well as a KOR agonist (Gustein et al. 2001). Nubain was approved for marketing in the United States in 1978 and remains as the only opioid analgesic of this type (marketed in the U.S.) not controlled under the Controlled Substances Act (CSA). When the Controlled Substances Act (CSA) was enacted in 1971, nalbuphine was placed in schedule II. Endo Laboratories, Inc.

Though often efficient and exhibiting useful or unique selectivities, there is considerable uncertainty with respect to the mechanism of processes catalyzed by various heterogeneous gold catalysts, even compared to other heterogeneous transition metal catalysts. In contrast, homogeneous catalysis with gold uses simple or ligand-bound gold(I) or gold(III) compounds that are soluble in organic solvents and is used for the synthesis of fine chemicals in organic chemistry.Gold catalysis for organic synthesis F. Dean Toste (Editor) Thematic Series in the Open Access Beilstein Journal of Organic Chemistry Binary gold halides and simple complexes, including gold(I) chloride, gold(III) chloride, and chloroauric acid, have been employed as complexes. These gold sources, however, quickly give rise to ill-defined and easily deactivated (via reduction to Au0) active catalysts in solution.

The core of Chirik's Earth-abundant metal catalysis program is the understanding and manipulation of electron flow, and its application to solving modern problems. Development efforts are specifically geared towards problems in the pharmaceutical, flavor, fragrance, petrochemical, and silicones industries. The broad catalysis concept of "metal-ligand cooperativity" popularized by Chirik, where electron changes occur concomitantly between the metal and the supporting ligand ("redox-active limit"), led to the development of Earth-abundant catalysts based on iron and cobalt for asymmetric hydrogenation, hydrosilylation, and hydroboration of olefins with superior activities and selectivities to their precious metal counterparts as well as catalysts for unprecedented cycloaddition reactions. Chirik has also developed Earth-abundant catalysts that operate in a more traditional sense, where the electron changes occur exclusively at the metal ("strong-field limit") with the judicious choice of the supporting ligand.

While the dimensions of the individual channels are small, a micro process engineering device ("microstructured reactor") can contain many thousands of such channels, and the overall size of a microstructured reactor can be on the scale of meters. The objective of micro process engineering is not primarily to miniaturize production plants, but to increase yields and selectivities of chemical reactions, thus reducing the cost of chemical production. This goal can be achieved by either using chemical reactions that cannot be conducted in larger volumina, or by running chemical reactions at parameters (temperatures, pressures, concentrations) that are inaccessible in larger volumina due to safety constraints. For example, the detonation of the stoichiometric mixture of two volume unit of hydrogen gas and one volume unit of oxygen gas does not propagate in microchannels with a sufficiently small diameter.

Similar to the controlled directionality of molecular machines, the resulting ratchet (device) energy mechanism selectively moves molecules through a catalytic reaction against a free energy gradient. Application of dynamic binding energy to a surface with multiple catalytic reactions exhibits complex behavior derived from the differences in the natural frequencies of each chemistry; these frequencies are identified by the inverse of the adsorption, desorption, and surface kinetic rate parameters. Considering a system of two parallel elementary reactions of A-to-B and A-to-C that only occur on a surface, the performance of the catalyst under dynamic conditions will result in varying capability for selecting either reaction product (B or C). For the depicted system, both reactions have the same overall thermodynamics and will produce B and C in equal amounts (50% selectivity) at chemical equilibrium. Under normal static catalyst operation, only product B can be produced at selectivities greater than 50% and product C is never favored.

The Hajos 1974 carbinolamine mechanism has had an unwitting support in a more recent paper by Michael Limbach.β-Homoamino acids as catalysts on enantioselective intra- and intermoelcular aldol reactions by Michael Limbach, Tetrahedron Letters 47 (2006) 3843-3847 The triketone starting material 2- methyl-2-(3-oxobutyl)-1,3-cyclopentanedione gave the expected optically active bicyclic ketol (+)-(3aS,7aS)-3a,4,7,7a-tetrahydro-3a-hydroxy-7a-methyl-1,5(6H)-indanedione with (S)-(−)-proline catalyst. On the other hand, the stereochemical outcome is reversed with ee selectivities of up to 83% by using the homologue amino acid catalysts, such as (S)-β-homoproline, [(pyrrolidine-(2S)-yl) acetic acid]. The virtual anomaly can be explained with a top side approach of the bulkier beta amino acids to the above triketone starting material of reflective symmetry. The top side approach results in the formation of an enantiotopic carbinolamine to give the (−)-(3aR,7aR)-3a,4,7,7a-tetrahydro-3a-hydroxy-7a-methyl-1,5(6H)-indanedione bicyclic ketol enantiomer identical to the one obtained with unnatural (R)-(+)-proline. List in 2010 on the other hand is perplexed and surprised that Hajos rejected the enamine mechanism, certainly in light of earlier work by Spencer in 1965 on amine catalysed aldol reactions.