The basic idea is that the people you feel most different from in childhood become the target of your later sexual attractions, with gender non-conformers tending toward same-sex attractions and gender conformers tending toward opposite-sex attractions.
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We break these groups into two overarching categories: "conformers" (individuals who are prone to obedience) and "colluders" (those who actively align themselves with toxic leaders).
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There are, however, procedures that will help with a patient's appearance, the National Eye Institute said, such as prosthetics or plastic conformers to help promote eye socket growth.
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In terms of conformers, "lost souls" are insecure individuals who lack a clear sense of self and who find a sense of identity, purpose and belonging through their affiliation with strong, powerful leaders and their groups.
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And so with conformers, employees who are lost souls or authoritarians are at greater risk of blind obedience to those in power – and being co-opted by another bad manager, thereby making it harder to fix the culture.
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It is hypothetically possible that two different conformers in equilibrium could react through transition states that are equal in energy. In this case, product selectivity would depend only on the distribution of ground-state conformers. In this case, both conformers would react at the same rate.
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The pentanenitrile molecule is flexible and can adopt a number of different conformers, so that it will naturally be a mixture. These conformers are called anti-anti (30%), anti-gauche (46%), gauche-anti, gauche-gauche-cis, and gauche-gauche-trans.
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Pyranose and furanose forms can exist in different conformers and one can interconvert between the different conformations if an energy requirement is met. For the furanose system there are two possible conformers: twist (T) and envelope (E). In the pyranose system five conformers are possible: chair (C), boat (B), skew (S), half-chair (H) or envelope (E). In all cases there are four or more atoms that make up a plane.
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Paraldehyde is produced and used as a mixture of two diastereomers, known as cis- and trans- paraldehyde. For each diastereomer, two chair conformers are possible. The structures (1), (4) and (2), (3) are conformers of cis- and trans-paraldehyde, respectively. The structures (3) (a conformer of (2)) and (4) (a conformer of (1)) are high energy conformers on steric grounds (1,3-diaxial interactions are present) and do not exist to any appreciable extent in a sample of paraldehyde.
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Alkane stereochemistry concerns the stereochemistry of alkanes. Alkane conformers are one of the subjects of alkane stereochemistry.
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There are also a variety of stable conformers due to the rotation of single bonds in the N-pyridylmethylamino group. The E-conformer is more stable than the Z-conformer and assumed to be the active form. In solution, two different E-conformers exist which slowly change into each other.
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Currently, there is not a treatment option for regaining vision by developing a new eye. There are, however, cosmetic options so the absence of the eye is not as noticeable. Typically, the child will need to go to a prosthetic specialist to have conformers fitted into the eye. Conformers are made of clear plastic and are fitted into the socket to promote socket growth and expansion.
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Another approach uses selection algorithms such as ENSEMBLE and ASTEROIDS. Calculation procedures first generate a pool of random conformers (initial pool) so that they sufficiently sample the conformation space. The selection algorithms start by choosing a smaller set of conformers (an ensemble) from the initial pool. Experimental parameters (NMR/SAXS) are calculated (usually by some theoretical prediction methods) for each conformer of chosen ensemble and averaged over ensemble.
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This method uses an appropriate algorithm (e.g. steepest descent) to find the molecular structure of a local energy minimum. These minima correspond to stable conformers of the molecule (in the chosen force field) and molecular motion can be modelled as vibrations around and interconversions between these stable conformers. It is thus common to find local energy minimization methods combined with global energy optimization, to find the global energy minimum (and other low energy states).
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The "strain energy" of a molecule is a quantity that is difficult to precisely define, so the meaning of this term can easily vary depending on one's interpretation. Instead, an objective way to view the allylic strain of a molecule is through its conformational equilibrium. Comparing the heats of formation of the involved conformers, an overall ΔHeq can be evaluated. This term gives information about the relative stabilities of the involved conformers and the effect allylic strain has on equilibrium.
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A solvated ligand that binds the protein of interest is likely to exist as an equilibrium mixture of several conformers. Likewise the solvated protein also exists as several conformers in equilibrium. Formation of protein-ligand complex includes displacement of the solvent molecules that occupy the binding site of the ligand, to produce a solvated complex. Because this necessarily means that the interaction is entropically disfavored, highly favorable enthalpic contacts between the protein and the ligand must compensate for the entropic loss.
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Note that the twist-boat (D2) conformer and the half-chair (C2) transition state are in chiral point groups and are therefore chiral molecules. In the figure, the two depictions of B and two depictions of D are pairs of enantiomers. As a consequence of the chair flip, the axially- substituted and equatorially-substituted conformers of a molecule like chlorocyclohexane cannot be isolated at room temperature. However, in some cases, the isolation of individual conformers of substituted cyclohexane derivatives has been achieved at low temperatures (–150 °C).
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Rapid equilibration between enantiomeric conformers and irreversible hydrogenation place the reaction under Curtin–Hammett control. The use of a chiral catalyst results in a higher-energy and a lower-energy transition state for hydrogenation of the two enantiomers. The transformation occurs via the lower-energy transition state to form the product as a single enantiomer. Consistent with the Curtin–Hammett principle, the ratio of products depends on the absolute energetic barrier of the irreversible step of the reaction, and does not reflect the equilibrium distribution of substrate conformers.
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When dopamine interacts with ATP, which is a component of some dopamine receptors, it has a significant preference for a trans-conformation of the dopamine molecule. The dopamine-ATP complex is stabilised by hydrogen bonding between catechol hydroxyls and purine nitrogens and by electrostatic interactions between the protonated ammonium group of dopamine and a negative phosphate group. Two conformers of dopamine have been identified as alpha- and beta-conformers in which the catechol ring is coplanar with the plane of the ethylamine side chain. They are substantial in agonist-receptor interactions.
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Understanding the stereochemistry of α-diazo ketones is essential in elucidating the mechanism of the Wolff rearrangement. α-diazocarbonyl compounds are generally locally planar, with large rotational barriers (55–65 kJ/mol) due to C-C olefin character between the carbonyl and α-carbon, illustrated in the rightmost resonance structure. Such a large barrier slows molecular rotations sufficiently to lead to an equilibrium between two conformers, an s-trans and s-cis-conformer. s-cis-Conformers are electronically favored due to Coulombic attraction between the oxygen with a partial negative charge and the cationic nitrogen, as seen in the rightmost resonance structure.
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The conformer of methylcyclohexane with equatorial methyl is favored by relative to the conformer where methyl is axial. In cyclohexane, the two chair conformations have the same energy. The situation is more complex is substituted derivatives. In methylcyclohexane the two chair conformers are not isoenergetic.
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Chemical substitutions on the bispidine backbone can influence the equilibrium of conformers. Many computational studies and others based on nuclear magnetic resonance (1H and 13C NMR), X-ray crystallography and Raman spectroscopy have been done to investigate the different conformational entities of bispidine derivatives.
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All organisms possess prolyl isomerase enzymes to catalyze this isomerization, and some bacteria have specialized prolyl isomerases associated with the ribosome. However, not all prolines are essential for folding, and protein folding may proceed at a normal rate despite having non-native conformers of many X-Pro peptide bonds.
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The interconversion of chair conformers is called ring flipping or chair-flipping. Carbon-hydrogen bonds that are axial in one configuration become equatorial in the other, and vice versa. At room temperature the two chair conformations rapidly equilibrate. The proton NMR spectrum of cyclohexane is a singlet at room temperature.
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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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Two chair conformations of cyclohexane. The entirety of axial positions become equatorial, and vice versa, upon ring flip. In organic chemistry, a ring flip (also known as a ring inversion or ring reversal) is the interconversion of cyclic conformers that have equivalent ring shapes (e.g., from a chair conformer to another chair conformer) that results in the exchange of nonequivalent substituent positions.
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Radiation of methoxyvinyl protons in free enone and in enone complexed with monodentate Ti(IV) show s-cis and s-trans conformations, while radiation of the enone in a bidentate Ti(IV) complex showed predominantly s-trans conformers. In 2003, this group extended the allylation strategy using this bidentate catalyst to ketones.Kii, S., Maruoka, K., Chirality, 2003, 15, 68-70.
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When cooled to cryogenic temperatures it can have different conformers, gauche and trans. In the liquid form these are about equally abundant and easily interconvert. As a gas it is mostly the gauche form. In the HFC-152 designation, 2 means two fluorine atoms, 5 means 5-1 or four hydrogen atoms, and 1 means 1+1 or two carbon atoms.
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While any two arrangements of atoms in a molecule that differ by rotation about single bonds can be referred to as different conformations, conformations that correspond to local minima on the energy surface are specifically called conformational isomers or conformers. Conformations that correspond to local maxima on the energy surface are the transition states between the local-minimum conformational isomers. Rotations about single bonds involve overcoming a rotational energy barrier to interconvert one conformer to another. If the energy barrier is low, there is free rotation and a sample of the compound exists as a rapidly equilibrating mixture of multiple conformers; if the energy barrier is high enough then there is restricted rotation, a molecule may exist for a relatively long time period as a stable rotational isomer or rotamer (an isomer arising from hindered single-bond rotation).
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Second, regardless of the reaction mechanism, the rearrangement gives a ketene intermediate, which can be trapped by a weakly acidic nucleophile, such as an alcohol or amine, to give the corresponding ester or amide, or an olefin, to give a [2+2] cycloaddition adduct. Strong acids do not rearrange, but rather protonate the α-carbon and give SN2 products. Concerted versus stepwise mechanism for ground state conformers.
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Neutral networks exist in fitness landscapes since proteins are robust to mutations. This leads to extended networks of genes of equivalent function, linked by neutral mutations. Proteins are resistant to mutations because many sequences can fold into highly similar structural folds. A protein adopts a limited ensemble of native conformations because those conformers have lower energy than unfolded and mis-folded states (ΔΔG of folding).
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The overall process generally takes place over several steps, involving coupled rotations about several of the molecule's single bonds, in conjunction with minor deformations of bond angles. Most commonly, the term is used to refer to the interconversion of the two chair conformers of cyclohexane derivatives, which is specifically referred to as a chair flip, although other cycloalkanes and inorganic rings undergo similar processes.
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Her lab currently works on modeling the stability of this radical and its conformers. Currently, her group focuses on photo-induced chemistry of Criegee intermediates, an intermediate in the alkene ozonolysis pathway. This pathway is a primary oxidation pathway for alkenes in the troposphere and generates atmospheric hydroxyl radicals. Her lab synthesizes Criegee intermediates in order to further study their chemical reactions using spectroscopy.
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The C4 ring of the cis isomer of CBDO is non-planar. For simple non-planar cyclobutanes, dihedral angles range from 19 to 31°. CBDO’s cis isomer crystallizes as two conformers with an average dihedral angle of 17.5° in the solid state.Shirrell & Williams "The crystal and molecular structure of cis-2,2,4,4-tetramethyl-1,3-cyclobutanediol" Acta Crystallographica Section B. 1976, Volume 32, pp. 1867-1870.
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Bicorannulenyl is the product of dehydrogenative coupling of corannulene. With the formula C20H9-C20H9, it consists of two corannulene units connected through a single C-C bond. The molecule's stereochemistry consists of two chiral elements: the asymmetry of a singly substituted corannulenyl, and the helical twist about the central bond. In the neutral state, bicorannulenyl exists as 12 conformers, which intercovert through multiple bowl-inversions and bond-rotations.
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Alpha-synuclein pathology is also found in both sporadic and familial cases with Alzheimer's disease. The aggregation mechanism of alpha-synuclein is uncertain. There is evidence of a structured intermediate rich in beta structure that can be the precursor of aggregation and, ultimately, Lewy bodies. A single molecule study in 2008 suggests alpha-synuclein exists as a mix of unstructured, alpha-helix, and beta-sheet-rich conformers in equilibrium.
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B. Fraser-Reid, Z. Wu, U. E. Udodong, H. Ottosson, J. Org. Chem. 1990, 55, 6068-6070. The concept has been extended to superarmed glycosyl donor by Mikael Bols and his collaborators. He realised that the hydroxy groups of carbohydrates are less electron-withdrawing towards the anomeric center when they are axial than when they are equatorial, which means that glycosyl donor conformers with more axial oxy functions are more reactive.
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Greenwood, 658 Two forms (α-, β-) of cyclo-S9 are known, one of which has been characterized.Steudel, 8 Two forms of cyclo-S18 are known where the conformation of the ring is different. To differentiate these structures, rather than using the normal crystallographic convention of α-, β-, etc., which in other cyclo-Sn compounds refer to different packings of essentially the same conformer, these two conformers have been termed endo- and exo-.
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The bound BIM1 inhibitor blocks the ATP-binding site and puts the kinase domain into an intermediate open conformation. The value of such calculations lies in understanding a variant was designed which showed improved binding characteristics of configurationally stable atropisomeric bisindolylmaleimides where the two kinase domains, and two different inhibitor conformers bind in different orientations, the hinge region of staurosporine- Pim-1 resembles co-crystallized as an asymmetric pair of biosynthetically 'related' indolocarbazole analogs.
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The boat conformation (C, 6.9 kcal/mol, C2v symmetry) is a local energy maximum for the interconversion of the two mirror image twist-boat conformers, the second of which is converted to the other chair confirmation through another half-chair. At the end of the process, all axial positions have become equatorial and vice versa. The overall barrier of 10.8 kcal/mol corresponds to a rate constant of about 105 s–1 at room temperature.
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Some of the substrate-bound conformations bear high similarity to the substrate-free ones, but they are not entirely identical, particularly in the AAA-ATPase module. Prior to the 26S assembly, the 19S regulatory particle in a free form has also been observed in seven conformational states. Notably, all these conformers are somewhat different and present distinct features. Thus, the 19S regulatory particle can sample at least 20 conformational states under different physiological conditions.
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Rotation about single bond of butane to interconvert one conformation to another. The gauche conformation on the right is a conformer, while the eclipsed conformation on the left is a transition state between conformers. Above: Newman projection; below: depiction of spatial orientation. In chemistry, conformational isomerism is a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds (refer to figure on single bond rotation).
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Protein mutation tolerance is the product of two main features: the structure of the genetic code and protein structural robustness. Proteins are resistant to mutations because many sequences can fold into highly similar structural folds. A protein adopts a limited ensemble of native conformations because those conformers have lower energy than unfolded and mis-folded states (ΔΔG of folding). This is achieved by a distributed, internal network of cooperative interactions (hydrophobic, polar and covalent).
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Coaxial stacking is the tendency of nucleic acid blunt ends to bind to each other, by interactions between the exposed bases. There are three possible conformers: an unstacked form and two stacked forms. The unstacked form dominates in the absence of divalent cations such as Mg2+, because of electrostatic repulsion between the negatively charged backbones of the strands. In the presence of at least about 0.1 mM Mg2+, the electrostatic repulsion is counteracted and the stacked structures predominate.
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In solution, reducing monosaccharides exist in equilibrium between their acyclic and cyclic forms with less than 1% in the acyclic form. The open chain form can close to give the pyranose and furanose with both the α- and β-anomers present for each. The equilibrium population of conformers depends on their relative energies which can be determined to a rough approximation using steric and stereoelectronic arguments. It has been shown that cations in solution can shift the equilibrium.
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The gauche effect is very sensitive to solvent effects, due to the large difference in polarity between the two conformers. For example, 2,3-dinitro-2,3-dimetylbutane, which in the solid state exists only in the gauche conformation, prefers the gauche conformer in benzene solution by a ratio of 79:21, but in carbon tetrachloride it prefers the anti conformer by a ratio of 58:42.Smith, Michael. B.; March, J. March's Advanced Organic Chemistry, 5th edition.
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The epoxidation of asymmetric alkenes has also been studied as an example of Curtin–Hammett kinetics. In a computational study of the diastereoselective epoxidation of chiral allylic alcohols by titanium peroxy complexes, the computed difference in transition state energies between the two conformers was 1.43 kcal/mol. Experimentally, the observed product ratio was 91:9 in favor of the product derived from the lower-energy transition state. This product ratio is consistent with the computed difference in transition state energies.
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This geometry is a local energy maximum, so in contrast to the s-trans geometry, it is not a conformer. The gauche geometry, in which the double bonds of the s-cis geometry are twisted to give a dihedral angle of around 38°, is a second conformer that is around 12.0 kJ/mol (2.9 kcal/mol) higher in energy than the s-trans conformer. Overall, there is a barrier of 24.8 kJ/mol (5.9 kcal/mol) for isomerization between the two conformers.
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PDE5 is an enzyme that accepts cGMP and breaks it down. Sildenafil, vardenafil and tadalafil are inhibitors of this enzyme, which bind to the catalytic site of PDE5. Both inhibitors bind with high affinity and specificity, and cGMP-binding to the allosteric sites stimulates binding of PDE5 inhibitors at the catalytic site. The kinetics of inhibitor binding and inhibition of catalysis imply the existence of two PDE5 conformers, and results of native gel electrophoresis reveal that PDE5 exists in two apparently distinct conformations, i.e.
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Schematic diagrams of the three base-stacking conformational isomers of the Holliday junction. The two stacked conformers differ in which sets of two arms are bound by coaxial stacking: at left, the stacks are red–blue and cyan–magenta, while at right the stacks are red–cyan and blue–magenta. The bases nearest to the junction point determine which stacked isomer dominates. Holliday junctions may exist in a variety of conformational isomers with different patterns of coaxial stacking between the four double-helical arms.
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A unique feature of DewA is its capacity to exist as two types of conformers in solution, both able to form rodlet assemblies but at different rates. Despite these differences in structural and self-assembly mechanisms, both EAS and DewA form robust fibrillar monolayers, meaning that there must exist several pathways, protein sequences and tertiary conformations able to self-assemble into amphipathic monolayers. Further characterisation of both EAS and DewA and their rodlet self-assembly mechanisms will open up opportunities for rational design of hydrophobins with novel biotechnological applications.
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When one is considering allylic strain, one needs to consider the possible conformers and the possible stereoelectronic demand of the reaction. For example, in the conformation of (Z)-4-methylpent-2-ene, the molecule isn't frozen in the favored conformer but rotates in the dihedral angle around 30° at <1kcal/mol cost. In stereoselective reactions, there are 2 effects of allylic strain on the reaction which is the sterics effect and the electronic effects. The sterics effect is where the largest group prefer to be the farthest from the alkene.
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It has been suggested that cephalopods do not osmoregulate, which would indicate that they are conformers. This means that they adapt to match the osmotic pressure of their environment, and because there is no osmotic gradient, there is no net movement of water from the organism to the seawater, or from the seawater into the organism. Octopuses have an average minimum salinity requirement of 27g/l, and that any disturbance introducing significant amounts of fresh water into their environment can prove fatal.Vaz-Pires, P., Seixas, P. & Barbosa, A. 2004.
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The chair and twist-boat are energy minima and are therefore conformers, while the half-chair and the boat are transition states and represent energy maxima. The idea that the chair conformation is the most stable structure for cyclohexane was first proposed as early as 1890 by Hermann Sachse, but only gained widespread acceptance much later. The new conformation puts the carbons at an angle of 109.5°. Half of the hydrogens are in the plane of the ring (equatorial) while the other half are perpendicular to the plane (axial).
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Oxygen, bright blue; nitrogen, red; sulfur, yellow; main chain, green These early structural studies were not followed up until recent years with the renewed interest in bottromycin. The structure was confirmed in the 1980s and 1990s to be a cyclic iminopeptide based on NMR studies, with a linear side chain connected to the macrocycle via an amidine linkage. Its absolute stereochemistry, however, was not characterized until 2009. Stereochemistry at carbon 18 and 25 was proposed by comparing predicted conformers obtained using molecular dynamics to experimental constraints obtained through NMR experiments.
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The term sandwich compound was introduced in organometallic nomenclature in 1956 in a report by J. D. Dunitz, L. E. Orgel and R. A. Rich, who confirmed the structure of ferrocene by X-ray crystallography. The correct structure had been proposed several years previously by Robert Burns Woodward and, separately, by Ernst Otto Fischer. The structure helped explain puzzles about ferrocene's conformers, the molecule features an iron atom sandwiched between two parallel cyclopentadienyl rings. This result further demonstrated the power of X-ray crystallography and accelerated the growth of organometallic chemistry.
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More recent work stresses the role of orbitofrontal cortex (OFC) in conformity not only at the time of social influence, but also later on, when participants are given an opportunity to conform by selecting an action. In particular, Charpentier et al. found that the OFC mirrors the exposure to social influence at a subsequent time point, when a decision is being made without the social influence being present. The tendency to conform has also been observed in the structure of the OFC, with a greater grey matter volume in high conformers.
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Priori Determination Of Favored Conformers - NMR Study Of Conformation Equilibrium. Bulletin De La Societe Chimique De France, 3616 The compound is decomposed by butyllithium with cleavage of the ring, and this reaction has been considered as a way of obtaining lithium enolates of aldehydes. In a superacid solution (--), the oxygen atom is protonated, and the carbon chain is split at the 3-4 bond, which gets replaced by bonds from carbons 3 and 4 to the oxygen atom. The formula of the resulting species could be written as (–()2C-CH2–)2.
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The mechanistic pathway of the Wolff-rearrangement has been the subject of much debate, as there are often competing concerted and stepwise mechanisms. However, two aspects of the mechanism can be agreed upon. First, α-diazocarbonyl compounds are in an equilibrium of s-cis and s-trans-conformers, the distribution of which may influence the mechanism of the reaction. Generally, under photolysis, compounds in the s-cis conformation react in a concerted manner due to the antiperiplanar relationship between the leaving and migrating groups, whereas compounds in the s-trans conformation react stepwise through a carbene intermediate or do not rearrange.
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As of 2000, it was not known with certainty whether the electrostatic shielding was the result of site-specific binding of cations to the junction, or the presence of a diffuse collection of the ions in solution. The unstacked form is a nearly square planar, extended conformation. On the other hand, the stacked conformers have two continuous double-helical domains separated by an angle of about 60° in a right-handed direction. Two of the four strands stay roughly helical, remaining within each of the two double-helical domains, while the other two cross between the two domains in an antiparallel fashion.
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Supercritical fluids act as a new media for the generation of novel crystalline forms of APIs (Active Pharmaceutical Ingredients) named as pharmaceutical cocrystals. Supercritical fluid technology offers a new platform that allows a single-step generation of particles that are difficult or even impossible to obtain by traditional techniques. The generation of pure and dried new cocrystals (crystalline molecular complexes comprising the API and one or more conformers in the crystal lattice) can be achieved due to unique properties of SCFs by using different supercritical fluid properties: supercritical CO2 solvent power, anti-solvent effect and its atomization enhancement.
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For example, one empirical study found that in the Netherlands, transgender people and other gender non-conforming LGBT people are often looked down upon within their communities for not acting "normal." Those who do assimilate often become invisible in society and experience constant fear and shame about the non-conformers within their communities. Stryker referenced theorist Jürgen Habermas and his view of the public sphere allowing for individuals to come together, as a group, to discuss diverse ideologies and by excluding the non-conforming LGBTQ community, society as a whole were undoubtedly excluding the gender-variant individuals from civic participation.
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Lactaldehyde is a three-carbon atom species with a carbonyl group on the first carbon atom (making it an aldehyde), and a hydroxy group on the second carbon atom, making it a secondary alcohol. The molecule is chiral, its stereocenter being located on the second carbon atom. Lactaldehyde exists in several forms: in open-chain form and as cyclic hemiacetal; in solution and in crystal forms; as monomer and as dimer. In crystal form, three conformers occur as hemiacetal dimers with a 1,4-dioxane ring skeleton: Dimerization of lactaldehyde leads to a mixture of stereoisomeric 1,4-dioxanes.
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Anti or syn indicates the substituents are on opposite sides or the same side, respectively. Clinal substituents are found within 30° of either side of a dihedral angle of 60° (from 30° to 90°), 120° (90°–150°), 240° (210°–270°), or 300° (270°–330°). Periplanar substituents are found within 30° of either 0° (330°–30°) or 180° (150°–210°). Juxtaposing the designations produces the following terms for the conformers of butane (see Alkane stereochemistry for an explanation of conformation nomenclature): gauche butane is syn-clinal (+sc or –sc, depending on the enantiomer), anti butane is anti-periplanar, and eclipsed butane is syn-periplanar.
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The word atropisomer (Gr., άτροπος, atropos, meaning "without turn") was coined in application to a theoretical concept by German biochemist Richard Kuhn for Karl Freudenberg's seminal Stereochemie volume in 1933. Atropisomerism was first experimentally detected in a tetra substituted biphenyl, a diacid, by George Christie and James Kenner in 1922. Michinori Ōki further refined the definition of atropisomers taking into account the temperature-dependence associated with the interconversion of conformers, specifying that atropisomers interconvert with a half-life of at least 1000 seconds at a given temperature, corresponding to an energy barrier of 93 kJ mol−1 (22 kcal mol −1) at 300 K (27 °C).
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The equation aids in the elucidation of protein folding as well as the conformations of other rigid aliphatic molecules. The equilibrium between conformational isomers can be observed using a variety of spectroscopic techniques. In cyclohexane derivatives, the two chair conformers interconvert with rapidly at room temperature, with cyclohexane itself undergoing the ring- flip at a rates of approximately 105 ring-flips/sec, with an overall energy barrier of 10 kcal/mol (42 kJ/mol), which precludes their separation at ambient temperatures. However, at low temperatures below the coalescence point one can directly monitor the equilibrium by NMR spectroscopy and by dynamic, temperature dependent NMR spectroscopy the barrier interconversion.
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It was observed that D2R exists in dimeric forms or higher order oligomers. There are some experimental and molecular modeling evidences that demonstrated the D2R monomers cross link from their TM 4 and TM 5 to form dimeric conformers. Oligomerization of D2R has a main role in their biological activities and any disordering in it may lead to mental diseases. It's known that the D2R ligands (either the agonist or antagonist) binding to the ligand-binding domain of D2R are independent of oligomerization and can not have any effect on its process, so the drugs used for the treatment of mental diseases can't cause any main problem in oligomerization of D2R.
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All women are underrepresented in STEM fields. While there has been a push to encourage more women to join the sciences, there is less outreach to lesbian, bi, or gender nonconforming women, and gender nonconforming people more broadly. Due to the lack of data and statistics of LGBTQ members involvement in the STEM field, it is unknown to what exact degree lesbian and bisexual women, gender non-conformers (transgender, nonbinary/agender, or anti-gender gender abolitionists who eschew the system altogether) are potentially even more repressed and underrepresented than their straight peers. But a general lack of out lesbian and bi women in STEM has been noted.
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The Curtin–Hammett principle is a principle in chemical kinetics proposed by David Yarrow Curtin and Louis Plack Hammett. It states that, for a reaction that has a pair of reactive intermediates or reactants that interconvert rapidly (as is usually the case for conformational isomers), each going irreversibly to a different product, the product ratio will depend both on the difference in energy between the two conformers and the energy barriers from each of the rapidly equilibrating isomers to their respective products. Stated another way, the product distribution reflects the difference in energy between the two rate-limiting transition states. As a result, the product distribution will not necessarily reflect the equilibrium distribution of the two intermediates.
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The database includes a web-based tool (the Morph server) which allows non-experts to animate and visualize certain types of protein conformational change through the generation of short movies. This system uses molecular modelling techniques to interpolate the structural changes between two different protein conformers and to generate a set of intermediate structures. A hyperlink pointing to the morph results is then emailed to the user. The Morph Server was originally primarily a research tool rather than general molecular animation tool, and thus offered only limited user control over rendering, animation parameters, color, and point of view, and the original methods sometimes required a fair amount of CPU time to completion.
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In practice methylphenidate is most commonly used as pairs of diastereomers rather than isolated single enantiomers or a mixture of all four isomers. Forms include the racemate, the enantiopure (dextro or levo) of its stereoisomers; erythro or threo (either + or -) among its diastereoisomers, the chiral isomers S,S; S,R/R,S or R,R and, lastly, the isomeric conformers (which are not absolute) of either its anti- or gauche- rotamer. The variant with optimized efficacy is not the usually attested generic or common pharmaceutical brands (e.g. Ritalin, Daytrana etc.) but the (R,R)-dextro-(+)-threo-anti (sold as Focalin), which has a binding profile on par with or better than that of cocaine.
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The two possible stacked forms differ in which pairs of the arms are stacked with each other; which of the two dominates is highly dependent on the base sequences nearest to the junction. Some sequences result in an equilibrium between the two conformers, while others strongly prefer a single conformer. In particular, junctions containing the sequence A-CC bridging the junction point appear to strongly prefer the conformer that allows a hydrogen bond to form between the second cytosine and one of the phosphates at the junction point. While most studies have focused on the identities of the four bases nearest to the junction on each arm, it is evident that bases farther out can also affect the observed stacking conformations.
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The effects of electrostatic and steric interactions of the substituents as well as orbital interactions such as hyperconjugation are responsible for the relative stability of conformers and their transition states. The contributions of these factors vary depending on the nature of the substituents and may either contribute positively or negatively to the energy barrier. Computational studies of small molecules such as ethane suggest that electrostatic effects make the greatest contribution to the energy barrier; however, the barrier is traditionally attributed primarily to steric interactions. Contributions to rotational energy barrier In the case of cyclic systems, the steric effect and contribution to the free energy can be approximated by A values, which measure the energy difference when a substituent on cyclohexane in the axial as compared to the equatorial position.
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D2R conformers are equilibrated between two full active (D2HighR) and inactive (D2LowR) states, while in complex with an agonist and antagonist ligand, respectively. The monomeric inactive conformer of D2R in binding with risperidone was reported in 2018 (PDB ID: 6CM4). However, the active form which is generally bound to an agonist, is not available yet and in most of the studies the Homology modeling of the structure is implemented. The difference between the active and inactive of G protein-coupled receptor is mainly observed as conformational changes at the cytoplasmic half of the structure, particularly at the transmembrane domains (TM) 5 and 6. The conformational transitions occurred at the cytoplasmic ends are due to the coupling of G protein to the cytoplasmic loop between the TM 5 and 6.
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Extensive VCD studies have been reported for both polypeptides and several proteins in solution; several recent reviews were also compiled. An extensive but not comprehensive VCD publications list is also provided in the "References" section. The published reports over the last 22 years have established VCD as a powerful technique with improved results over those previously obtained by visible/UV circular dichroism (CD) or optical rotatory dispersion (ORD) for proteins and nucleic acids. The effects due to solvent on stabilizing the structures (conformers and zwitterionic species) of amino acids and peptides and the corresponding effects seen in the vibrational circular dichroism (VCD) and Raman optical activity spectra (ROA) have been recently documented by a combined theoretical and experimental work on L-alanine and N-acetyl L-alanine N'-methylamide.
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During the interaction between HLA-F and the heavy chain (HC) of HLA class I molecules in activated lymphocytes, HLA-F plays a role as a chaperone, escorting HLA class I HC to the cell surface and stabilizing its expression in the absence of peptide. HLA-F binds most allelic forms of HLA class I open conformers, but it does not bind peptide complexes. The expression patterns of HLA-F in T cells suggest that HLA-F is involved in the communication pathway between T reg and activated T cells, where HLA-F signals that the immune response has been activated. During this communication, either HLA-F invokes secretion of inhibitory cytokines by the regulatory T cells or it provides a simple inhibitory signal to the regulatory T cells, allowing a normal immune response to proceed.
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The ability to maintain homeostasis at varying temperatures is the most important characteristic in defining an endothermic eurytherm, whereas other, thermoconforming eurytherms like tardigrades are simply able to endure significant shifts in their internal body temperature that occur with ambient temperature changes. Eurythermic animals can be either conformers or regulators, meaning that their internal physiology can either vary with the external environment or maintain consistency regardless of the external environment, respectively. It is important to note that endotherms do not solely rely on internal thermogenesis for all parts of homeostasis or comfort; in fact, in many ways, they are equally as reliant upon behavior to regulate body temperature as ectotherms are. Reptiles are ectotherms, and therefore rely upon positive thermotaxis, basking (heliothermy), burrowing, and crowding with members of their species in order to regulate their body temperature within a narrow range and even to produce fevers to fight infection.
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Various combinations of electron-withdrawing substitutions in the aniline ring of these drugs have not shown higher binding to the AR receptor, compared to compounds which have a chloro or trifluoromethyl group at the meta position (R1) and either a cyano or nitrogen group at the para position (R2). For hydroxyflutamide, a group of compounds that differed in the aromatic ring did not bind to the AR. This suggests that the bisubstitution in the hydroxyflutamide ring is essential for high AR binding affinity. It has also been demonstrated that hydroxyflutamide requires the strong hydrogen bond donor ability of the tertiary hydroxyl group and fixed conformers involved in intramolecular hydrogen binding, to bind effectively to AR. For bicalutamide, the antiandrogenic activities of sulfide and sulfone substitutions of the X-linkage were tested in vitro. The sulfides showed in most cases at least 2-fold higher binding affinity than corresponding sulfones.
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