Systematic Estimates for Possible Regular Helix Models of Heteropolymeric Glucans, Elsinan and Lichenan, Using N-H Mapping Method

Regular helical structures of polysaccharides are most conveniently described by a set of the helix parameters; n for the number of chemical repeating units per turn and h in A for the rise per unit along the helix axis. A two dimensional mapping of n-h values for possible helix models along with the potential energy surfaces allows one to estimate conformational accessibility of a given posaccharide.1-3 Recently, we have adopted the method to study an acidic heteropolysaccharide4 and a branching glucan.5 These polysaccharides involve two or three sets of backbone glycosidic linkages (Φ-Ψ), each of which varies independently, and, therefore, enormous multidimensional spaces must be explored. Their n-h maps were calculated based on the low energy Φ-Ψ values derived from MM36-8-generated, relaxed-residue potential energy maps9, 10 of the component disaccharides. The present assessment of helix models for the two heteropolymeric glucans is achieved by calculating n-h maps in a similar fashion. These glucans ...