Solution properties of an α-(1→3)-D-glucan from Lenthius edodes and its sulfated derivatives

A water-insoluble alpha-(1-->3)-D-glucan (A) from Lentinus edodes was fractionated into 13 fractions in dimethyl sulfoxide containing 0.25 M lithium chloride (0.25 M LiCl-Me2SO). Five fractions were treated with sulfur trioxide-pyridine complex at 25degreesC to synthesize water-soluble sulfated derivatives (S-A). The weight-average molecular weights, M-w, and intrinsic viscosities [eta], of the samples A and S-A were determined by multi-angler laser light scattering (MALLS), and viscosity. The M-w dependence of [eta] and of the radius of gyration (1/2)(z), was found to be represented approximately by [eta] = 4.9 x 10(-2) M-w(0.67) (cm(3) g(-1)), and (1/2)(z) = 4.8 x 10(-2) M-w(0.54) (nm) for the alpha-glucan in 0.25 M LiCl-Me2SO in the M-w range from 7.24 x 10(4) to 4.21 x 10(5), and by [eta] 6.8 x 10(-4) M-w (106) (cm(3) g(-1)), and (1/2)(z) = 9.4 x 10(4) M(w)(0.92 ()nm) for the sulfated alpha-glucan in aqueous 0.5 M NaCl in the M-w range from 5.92 x 10(4) to 1.42 x 10(5) at 25degreesC. The results indicate that the alpha-(1-->3)-D-glucan exists as a flexible chain in 0.25 M LiCl-Me2SO, and its sulfated derivative in 0.5 M NaCl aqueous has stiffer chains than the original, C-13 NMR indicated that intramolecular hydrogen bonding occurred in the sulfated a-glucan, causing the observed chain stiffness. (C) 2002 Elsevier Science Ltd. All rights reserved.