Flexible chain conformation of (1→3)-β-D-glucan from Poria cocos sclerotium in NaOH/urea aqueous solution

摘要

A water-insoluble polysaccharide (PCS3-II) extracted from sclerotium of Poria cocos was identified as a linear (1→3)-β-D-glucan by ~(13)C NMR and gas chromatography. Aqueous 0.5 M NaOH/0.2 M urea was a good solvent for PCS3-II and the dependence of intrinsic viscosity ([η]) on weight-average molecular weight (M_w) was established in the M_w range from 7.68 x 10~4 to 5.14 x 10~5 to be [η] = 3.39 x 10~(-2) M_w~(0.62) cm~3g~(-1) at 25 °C by using laser light scattering and viscometry. The chain conformation parameters of PCS3-II in the 0.5 M NaOH/0.2 M urea solution was 2.3 (±0.3)nm for persistence length (q), 580 g mol~(-1) nm~(-1) for molar mass per unit contour length (M_L), 0.8 (± 0.2) nm for the diameter of the chain (d) and 3.63 for limited characteristic ratio (C_∞). The results revealed, for the first time, that PCS3-I1 existed as a flexible chain in 0.5 M NaOH/0.2 M urea aqueous solution.