Disaccharides angles

The side chains in the latter are flexible disaccharides on account of poor-quality diffraction patterns, their tentative molecular structures are known only from computer modeling.1" On the other hand, well-defined crystal structures are available for gellan and welan, and they can be correlated with the physical properties of the polysaccharides the details are presented here. Their conformation angles are listed in Table VI. 

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). 

Our procedure depends on a new computer program, RAMM (RAndom Molecular Mechanics), which is applicable to any kind of biomolecule. It is described in detail elsewhere (KoS r, T./ Petrak, F. Galova, Z. TvaroSka, I. Carbohvdr. Res.. in Press). Only the basic characteristics of RAMM and its application to conformational analysis of disaccharides are discussed here, concentrating on the effect of the orientations of pendant groups on the energy values at the various < ) and f torsion angles. 

The orientation of the pendant groups in a disaccharide coitqposed of two hexapyranose residues can be described by 10 torsion angles. 

Figure 1. A (1 -> 4) disaccharide showing and < ), based on the torsion angles Hl-Cl-04 -C4 and Cl-04 -C4 -H4, respectively.

As shown in Table II, the optimal value of the rotation angle per disaccharide unit around the helix axis, for a free... 

---