Preparation and characterization of molecular weight fractions of glycosaminoglycan from sea cucumber Thelenata ananas using free radical depolymerization

A glycosaminoglycan from sea cucumber Thelenata anana (THG) was isolated as a polymer of molecular weight of around 70 kDa. Its low molecular weight derivatives were first prepared by free radical depolymerization with hydrogen peroxide in the presence of copper(II) ion. The parameters of the process were investigated by a high-performance gel permeation chromatography. Analyses of chemical composition and molecular weight distribution indicated that the fragmentation of the main-chain of THG occurred randomly, obeyed pseudo first-order kinetics, and produced species with rather narrow and unimodal distribution of molar mass. The characterization of different molecular weight fractions was investigated by using viscometry and atomic force microscopy (AFM). Analysis of molecular weight and intrinsic viscosity in terms of the known theories for unperturbed wormlike cylinder yielded 1201 ± 110 nm⁻¹, 15.3 ± 1.5 nm, and 1.5 ± 0.3 nm for molar mass per unit contour length M_L, persistence length q, and diameter d, respectively. The M_L and d values were approximately consistent with those observed by AFM. The present data suggest that THG may dissolve in 0.1 M aqueous NaCl as single-stranded helical chains.