title: The reactivity of various free radicals with hyaluronic acid: steady-state and pulse radiolysis studies.
abstract: The reactions of the primary water radicals with the biopolymer hyaluronic acid have been studied by pulse radiolysis. Bimolecular rate constants, expressed in terms of the disaccharide repeating sub-unit of hyaluronic acid, for OH., H. and eaq- were found to be 7 X 10(8) M-1 X s-1, 5 X 10(7) M-1 X s-1 and less than 5 X 10(6) M-1 X s-1, respectively. By comparing the viscosities of samples, gamma-irradiated in the steady state under a variety of conditions, with unirradiated controls, the efficiencies with which selected radicals cause chain breakage have been determined. Efficiencies of 30%, 15%, 0%, 0.2% and 5% were estimated for OH., H., eaq-, methanol radicals and tert-butanol radicals, respectively. The presence of oxygen during irradiation increased the extent of chain breakage by a factor of 1.75.
mesh_terms: D004583:Electrons; D005609:Free Radicals; D005720:Gamma Rays; D006820:Hyaluronic Acid / Q000528:radiation effects*; D006878:Hydroxides; D010100:Oxygen; D011522:Protons; D011854:Radiochemistry; D014783:Viscosity; D014867:Water
chemical_list: D005609:Free Radicals; D006878:Hydroxides; D011522:Protons; D014867:Water; D006820:Hyaluronic Acid; D010100:Oxygen