Conformation solution state

From X-ray diffraction experiments28 it is known that in the crystalline phase the erythrodiisotactic poly(l,2-dimethyltetramethylene) has a (g+aaa g aaa)n structure as shown in Fig. 13. The bold printed letters in the denotation give the conformation of the CH—CH bond. In agreement with this structure and low temperature solution state spectra of 2,3-dimethylbutane, 3,4-dimethylhexane, and 4,5-dimethyloctane 29 30) in which the CHCH bond rotation is frozen the crystalline signals can be assigned conclusively. Like for the crystalline state of poly(l,2-... 

The practice of including the conformation after the name of the parent monosaccharide should be used only with caution because not all conformations are known with certainty. In the case of furanose rings especially, conformations might differ between the crystalline and solution states. 

The long side chains of a homopolypeptide have remarkable motional freedom about multiple bonds, while the main chain forms the secondary regular conformation such as a-helix, /1-sheet, and turn, which are rigid structures. The macroscopic properties of the rigid a-helical polypeptide, therefore, highly depends on the dynamic structure of the side chains so that a lot of studies on the side chain dynamics of the a-helical polypeptides have been carried out in the solid and solution states.12,14,29 66... 

The original postulation of general acid catalysis by tyrosine-248 rested on closeness of that group to the amide function of the substrate in the crystal. However, the conformation in the crystal and solution states may be different in regard to the position of tyrosine-248 (Riordan and Muszynska, 1974). Thus, mechanistic inferences concerning that group may not be warranted. 

Fickett in "Detonation Properties of Condensed Explosives Calculated with an Equation of State Based on Intermolecular Potentials , Los Alamos Scientific Lab Rept LA-2712 (1962), pp 34-38, discusses perturbation theories as applied to a system of deton products consisting of two phases one, solid carbon in some form, and the other, a fluid mixt of the remaining product species. He divides these theories into two classes conformal solution theory, and what he chooses to call n-fluid theory. Both theories stem from a common approach, namely, perturbation from a pure fluid whose props are assumed known. They differ mainly in the choice of expansion variables. The conformal solution method begins with the assumption that all of the intermolecular interaction potentials have the same functional form. To obtain the equation of state of the mixt, some reference fluid obeying a common reduced equation of state is chosen, and the mixt partition function is expanded about that of the reference fluid... 

Phosphoglycerate kinase has been studied in both the crystal49 and solution states.50 When ATP binds to the enzyme in the crystal, little conformational change was observed. However, the protein was crystallized from sulfate, and the binding of ATP can perhaps be represented as... 

Ascidiacyclamide (14), a cytotoxic, cyclic peptide, was isolated from an unidentified species of ascidian [40], The absolute configuration was determined and the structure confirmed by total synthesis [41]. An X-ray crystal structure was carried out [42] and further X-ray crystallographic studies determined the conformation of the molecule in the solid- and solution-states [43]. 

Diaminopropane complexes [PdCl2(NH2CH2CHXCH2NH2)] e.g. X = OH) exist in different crystal forms where the polymorphism is thought to be due to different conformations of the chelate ring.201,202 The solution state equilibria have been studied by NMR spectroscopy.203... 

There are several reasons for reservations about applying the computer extrapolation of crystal structure data for carbohydrates. One is that much of the crystal structure data refer to unsubstituted sugars which are only soluble in hydroxylic or polar solvents where the conformational analysis may be complicated by hydrolysis, isomerism (muta-rotation) (12), or stereospecific solvent interactions which require a more sophisticated model. However, assuming that such chemical changes do not occur or can be suppressed, there still remain questions to be answered before the conformation observed in the crystal can be accepted as a close enough approximation to that of one or more of the rotomers which may predominate in the solution state. (a-L-Sorbose gives an example of the coexistence of two primary alcohol rotameric... 

Solid state analysis of crystals obtained of receptor with acetate from water/methanol solutions reveal that once again the guanidiniocarbonylpyrrole cation exists in an extended conformation however in contrast to the proposed solution state model, the pyrrole NH points away from the guanidium NHs with the acetate anions bound by two separate receptor groups with solvent molecules helping to create a series of 2D arrays (figure 23c). 

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