Triple helix and random coil of scleroglucan in dilute solution

Abstract

Eleven sonicated samples of a polysaccharide scleroglucan (chemically identical with but different in biological origin from schizophyllan) in 0.01n sodium hydroxide (naoh) and dimethylsulfoxide (dmso) at 25°;c were studied by light scattering, viscometry, and ultracentrifu-gation. data for the radius of gyration 〈s2〉1/2, the intrinsic viscosity [η], and the sedimentation coefficient s0 as functions of weight-average molecular weight mw, combined with those for the ratio mw (0.01n naoh)/mw (dmso), showed that scleroglucan dissolves in dmso as a single randomly coiled chain very similarly to that of schizophyllan in the same solvent, while it dissolves in 0.01n naoh as a rodlike trimer or higher aggregates, depending on whether mw (dmso) is lower or higher than 2×105. from 2, [η], and s0 for samples with mw (dmso)1×105 in 0.01n naoh, the contour length per main chain residue and the diameter of the scleroglucan trimer rod were found to be 0.30±0.03 and 2.6±0.5 nm, respectively, which agree with the reported pitch (per residue) and diameter of the schizophyllan triple helix. thus, it was concluded that the scleroglucan trimer has essentially the same triple helical structure as that of the schizophyllan trimer. evidence was obtained showing that the higher aggregates in 0.01n naoh consist of trimers as building units. © 1983 The Society of Polymer Science, Japan.