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

A water-insoluble polysaccharide (PCS3-II) extracted from sclerotium of Poria cocos was identified as a linear (1 -> 3)-beta-D-glucan by C-13 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 ([eta]) on weight-average molecular weight (M-w) was established in the M, range from 7.68 x 10(4) to 5.14 x 10(5) to be [eta] = 3.39 x 10(-2) M-W(0.62) cm(3) g(-1) at 25 degrees 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-infinity). 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. (C) 2008 Elsevier Ltd. All rights reserved.