A general treatment of the configuration statistics of polysaccharides

A treatment of the configurational statistics of polysaccharides is given in the isomeric state approximation. All classes of linear polysaccharides of specifiec chemical sequence are treated simultaneously. Chain tortuosity arising from torsional motions about the chemical bonds of the glycosidic linkages is recognized explicitly as is the possibility for conformational isomerism of the sugar residues. Valence angles and lengths are taken to be fixed at the equilibrium values, and pyranose residues in their chair conformations are treated as inflexible constituents of the skeletal structure. Pyranose and furanose forms capable of pseudorotation may be incorporated as rigid skeletal entities as well, provided suitable attention is given to the selection and interpretation of the conformational isomeric states included. Separation of the configuration energy into independent contributions is shown to be impossible in general. Methods are described for assessing the influence of neighbor interactions on the populations of the several conformers of the sugar residues. The relative conformational free energy of the flexible and chair form conformers of pyranose sugars is discussed, and appropriate measures of polysaccharide chain flexibility and stiffness are suggested.