Conformational properties of a bioactive polysaccharide from Ganoderma atrum by light scattering and molecular modeling

A bioactive polysaccharide from Ganoderma atrum (PSG-1-F-0.2) was previously characterized as a hyper-branched acidic beta-(1 -> 3)-glucan with long beta-(1 -> 6)-glucose side chains. The conformational properties of PSG-1-F-0.2 were systematically investigated by high performance size exclusion chromatography (HPSEC), light scattering, atomic force microscope (AFM) and molecular modeling techniques. Large aggregates were found when PSG-1-F-0.2 dissolved in pure water, while 0.9% NaCl solution exhibited the ability to reduce/eliminate the aggregates. The weight average molecular weight (Mw), radius of gyration (Rg), hydrodynamic radius (R-h) and intrinsic viscosity [eta] were determined as 12.73 kDa, 17.1 nm, 8.1 nm and 0.09 dL/g, respectively. The conformation analysis and AFM results together indicated that PSG-1-F-0.2 exhibited as hyper-branched compact spherical conformation in 0.9% NaCl solution. The results of molecular modeling identified that long beta-(1 -> 6)-glucose side chain played an important role in the aggregation and spherical conformation of PSG-1-F-0.2.