Solution properties of pachyman from Poria cocos mycelia in dimethyl sulfoxide

A linear beta-(1 -->3)-D-glucan PCM3 (pachyman), a major polysaccharide in Poria cocos mycelia, formed aggregates in aqueous solution or dimethyl sulfoxide (DMSO) with absorbed moisture, thereby considerably complicating its fractionation and study of solution properties. In this work, the pachyman PCM3 having narrow polydispersity (M-W/M-n = 1.9) was carefully fractionated by a preparative size exclusion chromatography (SEC) using dehydrated DMSO as the mobile phase. The weight-average molecular mass M-W and intrinsic viscosity [eta] Of the fractions were measured by static and dynamic laser light scattering, SEC combined with light scattering, and viscometry in DMSO at 25 degreesC, thus eliminating the aggregation. The Mark-Houwink equation for the pachyman in DMSO is established to be: [eta] = 6.79 x 10(-4) M-W(0.95) (mL/g) in the M-W range from 1.2 to 3.5 x 10(5). The characteristic ratio C-infinity of the PCM3 in DMSO at 25 degreesC, from light scattering by using Flory theory, was obtained to be 10.1, thus indicating that it behaves as a relatively expanded, flexible coil. In addition, the M-W of the pachyman from Poria cocos mycelia was 1.68 x 10(5), obviously larger than that from the sclerotium (8.9 x 10(4)).