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

Abstract

A water-insoluble polysaccharide (PCS3-II) extracted from sclerotium of Poria cocos was identified as a linear (1 → 3)-β- d-glucan by 13C 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 × 10 4 to 5.14 × 10 5 to be [ η] = 3.39 × 10 −2 M W 0.62 cm 3 g - 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-II existed as a flexible chain in 0.5 M NaOH/0.2 M urea aqueous solution.