Cationic dye binding by hyaluronate fragments: dependence on hyaluronate chain length.

Sodium hyaluronate, digested with bovine testicular hyaluronidase, yielded a mixture of oligosaccharides with identical repeating disaccharide structures and differing molecular weights. The oligosaccharides were separated into a ladder-like series of bands by electrophoresis on a 10% polyacrylamide gel matrix. Coelectrophoresis of purified oligosaccharides has established that adjacent bands differ in chain length by one disaccharide unit. This procedure formed the basis for a rapid screening method in which the binding of cationic dyes by hyaluronate oligosaccharides may be assayed. As a function of chain length, the oligosaccharides showed a marked change in dye binding. Species containing less than seven repeating disaccharide units are not detected by any dye tested, even at very high sample loads. Larger oligosaccharides show an increase in dye binding. The chain length at which constant maximal dye binding is reached depends on the dye structure and solvent conditions, varying from approximately 12 to 30 disaccharide units. The hyaluronate fragments of sufficient chain length to duplicate polymer behavior should be useful models for the study of hyaluronate structure and interactions in solution.