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

Abstract

A water-insoluble (1→3)- α- 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 25 °C. The dependences of intrinsic viscosity [ η] and radius of gyration 〈 s 2〉 z 1/2 on weight-average molecular mass M w for this glucan were found to be [ η]=(9.77±0.1)×10 −3 M w 0.77±0.02 (cm 3 g −1) and 〈 s 2〉 z 1/2=(1.83±0.4)×10 −2 M w 0.58±0.04 (nm) in the range of M w from 4.16 to 29.0×10 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 ∞), suggesting that the (1→3)- α- d-glucan exists as a relatively extended flexible chain in the 0.25 M LiCl/DMSO solution.