Chain conformation of sulfated derivatives of β-glucan from sclerotia of Pleurotus tuber-regium

Six water-insoluble (1-->3)-beta-D-glucan fractions TM8-1 to TM8-6 with weight-average molecular mass M-w ranging from 5.76 to 77.4 x 10(4) obtained from the sclerotia of Pleurotus tuber-regium were sulfated to produce the water-soluble fractions S-TM8-1 to S-TM8-6 with M-w from 6.0 to 64.8 x 10(4). The degree of substitution (DS) of S-TM8 fractions was analyzed by elemental analysis (EA) to be 1.14-1.74. The C-13 NMR results indicated that the C-6 was fully substituted, and C-2, C-4 were partially substituted by the sulfo-groups. The Mw and the intrinsic viscosity [eta] of the S-TM8 fractions were measured, respectively, by size-exclusion chromatography combined with laser light scattering (SEC-LLS), LLS and viscometry in phosphate buffer solution (PBS) at 37 degreesC. The dependences of [eta] and radius of gyration <s(2)>(1/2)(z) on M-w for the S-TM8 samples were found to be [eta] = 1.89 x 10(-2) M-w(0.70) (cm(3)/g) and <s(2)>(1/2)(z) = 1.12 x 10(-4) M-w(0.81) (nm) in the M-w range tested. Based on current theories for a wormlike chain model, the molar mass per unit contour length M-L and persistence length q of the S-TM8 were calculated to be 990 nm(-1) and 8.5 nm, respectively. The relatively higher q value suggested a more expanded flexible chain of S-TM8 in PBS. The water-solubility and relatively expanded chain conformation of the STM8 fractions were considered to be significant to their antiviral activity. (C) 2003 Elsevier Ltd. All rights reserved.