Solution properties of a water-insoluble (1→3)-α-D-glucan isolated from Poria cocos mycelia

A water-insoluble (1-->3)-alpha-D-glucan (wc-PCM3-I) was isolated from the Poria cocos mycelia by extracting with 0.5 M NaOH aqueous solution at room temperature. wc-PCM3-I dissolved in dimethylsulfoxide (DMSO) containing 0.25 M LiCl was fractionated by a nonsolvent addition method into 10 fractions, and the solution properties of seven of them were studied by size exclusion chromatography combined with laser light scattering and viscometry at 25degreesC. The dependences of intrinsic viscosity [eta] and radius of gyration <s(2)>(1/2)(z) on weight-average molecular mass M-w for this glucan were found to be [eta]=(9.77+/-0.1)x10(-3) M-w(0.77+/-0.02) (cm(3) g(-1)) and <s(2)>(1/2)(z) = (1.83+/-0.4)x10(-2) M-w(0.58+/-0.04) (nm) in the range of M-w from 4.16 to 29.0x10(4). On the basis of current theories for wormlike chain model, the conformation parameters of wc-PCM3-I were calculated to be 690 (nm(-1)) for molar mass per unit contour length (M-L), 4.5 (nm) for persistence length (q), and 11.9 for characteristic ratio (C-infinity), suggesting that the (1-->3)-alpha-D-glucan exists as a relatively extended flexible chain in the 0.25 M LiCl/DMSO solution. (C) 2004 Elsevier Ltd. All rights reserved.