Characterization of a polysaccharide–protein complex from Ganoderma tsugae mycelium by size-exclusion chromatography combined with laser light scattering

Abstract

A water-soluble polysaccharide–protein complex (GM3) extracted from the mycelium of Ganoderma tsugae was characterized using size-exclusion chromatography combined with laser light scattering (SEC-LLS). Two peaks coded as fractions I and II appeared in the SEC pattern of GM3 in 0.5 M NaCl aqueous solution, corresponding to the weight-average molecular mass ( M w) of 355×10 4 and 6.3×10 4, respectively. The relationship between the radius of gyration (< s 2> z 1/2) and M w showed that molecules of fraction I exhibited more compact coil conformation than that of fraction II in 0.5 M NaCl aqueous solution at 25 °C. To clarify the component of polysaccharide and protein in each fraction, the sample GM3 was treated with 0.2 M NaOH aqueous solution to degrade polysaccharide and trypsin to hydrolyze protein. The obtained products were analyzed by SEC combined with detectors such as UV, differential refractive index (DRI) and LLS. The results indicated that both the fractions I and II were protein-bound polysaccharide, but had different protein content and degree of branching, resulting in the difference of the chain conformation.