NMR studies of oligosaccharides derived from hyaluronate: complete assignment of 1H and 13C NMR spectra of aqueous di- and tetra-saccharides, and comparison of chemical shifts for oligosaccharides of increasing degree of polymerisation

Abstract

A series of oligosaccharides was prepared from hyaluronate by depolymerisation with bovine testicular hyaluronidase. Complete assignment of the 1H and 13C NMR spectra was obtained for the disaccharide, the tetrasaccharide, and the NaBH4-treated tetrasaccharide, by using various 1D and 2D NMR methods. The 1H assignments for the tetrasaccharide differ from the incomplete data reported recently (ref. 11). The 13C NMR spectra of the aqueous di-, tetra-, hexa-, and octa-saccharides of this series show that all resonances, apart from those subject to obvious end effects, have chemical shifts comparable to those of the corresponding resonances of hyaluronate in D2O. The observed 13C chemical shifts suggests that cooperative intramolecular hydrogen bonds probably play a minor role in determining the conformation of hyaluronate in water.