Measurements of reducing end groups on bovine vitreous-humour hyaluronic acid by reaction with [14C]cyanide.

Bovine vitreous-humour sodium hyaluronate was purified by precipitation with cetylpyridinium chloride, CsCl-density-gradient sedimentation and gel-permeation chromatography. The number of reducing end groups in two similarly prepared hyaluronate samples was determined by reaction with K14CN, and measurements of intrinsic viscosity were performed to determine whether this reaction caused degradation of the hyaluronate. The intrinsic viscosity of one hyaluronate sample was 192ml/g, compared with a value of 187ml/g after reaction with [14C]cyanide, which indicates that the labelling reaction did not cause depolymerization of the hyaluronate. The Mr calculated from these viscosity values is approx. 60000. Fractionation of the [14C]cyanide-labelled hyaluronate by gel chromatography showed that it was composed of a polydisperse population of molecules with calculated chain lengths, based on the ratio of [14C]cyanide to uronic acid, ranging in molecular weight from 9000 to 264000, with an average Mr of 63200. On the basis of these measurements it is concluded that reaction with [14C]cyanide does not cause degradation of bovine vitreous-humour hyaluronate polysaccharide chains and that reaction with [14C]cyanide can be used to determine the molecular weight of this hyaluronate.