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

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 〈s2〉z1/2 on weight-average molecular mass Mw for this glucan were found to be [η]=(9.77±0.1)×10−3Mw0.77±0.02 (cm3 g−1) and 〈s2〉z1/2=(1.83±0.4)×10−2Mw0.58±0.04 (nm) in the range of Mw from 4.16 to 29.0×104. 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 (ML), 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.