Torsion angles linkages

P212121 Z = 4 D, = 1.413 R = 0.041 for 3,165 intensities. Thepyran-oside conformation is 4C1, with Q = 58 pm, 6 = 5°. The primary alcohol group is gauche-trans. The linkage-bond torsion-angles are O-5-C-l-0-1 -C-7 = — 87°, C-1-0-1-C-7-0-7 = — 67°. The two rings of the monoterpene moiety are inclined to each other, with C-C-C-C torsion-angles, about the common bond, of 149 and —97°. 

C5 , then the atom is said to be endo, and if it is on the opposite side it is defined as exo. The conformation about the sugar-base linkage is defined as anti when the torsion angle (chi, 04 -Cl -Nl -C2 for pyrimidines and 041-Cl -N9-C4 for purines) lies near 180° and syn when it lies near 0°. These situations are illustrated in Figure 22. The glycosidic linkage are all anti in B-DNA and A-DNA, but in Z-DNA the guanine bases are in the syn conformation. 

While most CA s of disaccharides have depended only on intrinsic characteristics of the molecule, experimental results depend strongly on the environment. By experiment, Kamide and Saito ( ) have shown that the degree of flexibility of cellulose and its derivatives is strongly dependent on the dielectric constant of the solvent as well as the exact type and degree of substitution. Since a substantial portion of the polymer flexibility depends on the extent of variability of the torsion angles at the intermonomer linkage, the dependence of polymer flexibility on type of solvent and substitution means that the disaccharide flexibility also should depend on those factors. Non-polar solvents allowed the molecules to have greater flexibility than did polar solvents (35). 

Figure 2. Two maltotetraose models constructed from residues of glucose having different D. They have identical linkage bond and torsion angles.

The geometrical parameters of 1 were based on the standard structures of hexopyranoses ( ). The glycosidic linkage is described by the two torsion angles... 

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