Chain length distribution and aggregation of branched (1→3)-β-D-glucans from Saccharomyces cerevisae

Water-soluble (1→3)-β-D-glucans with 1,6-linked branches (SBG), originally isolated from the cell walls of Saccharomyces cerevisiae and partially depolymerised for optimal performance in wound healing applications, were studied by size exclusion chromatography (SEC) with multi-angle laser light scattering (MALLS) detector and a viscosity detector at both high and ambient column temperatures. The strongly aggregating materials could be dispersed as single chains in water following partial carboxymethylation (degree of substitution (DS) 0.51 or higher). Lower DS (0.23) also dispersed as single chains provided a column temperature of 80 °C was applied. Reduction of reducing ends prior to carboxymethylation was required to avoid alkaline peeling and hence to obtain correct molecular weight distributions of the native material. DS was determined using (13)C NMR and potentiometric titration (range 0.23-0.91). Further analysis of CM-SBG in the single chain state suggested a randomly coiled behaviour with marginal influence of the branches in terms of macromolecular dimensions, which were close to those of CM-curdlan. The result of the investigation is a simple and reliable protocol for preparing undegraded and un-aggregated SBG derivatives, which are well suited as a standard analysis of the molecular weight distribution of SBG-like molecules.