Transient Intermediates in the Radiolysis of Hyaluronic Acid

By means of electron paramagnetic resonance (EPR) after γ-irradiation in the solid state, hyaluronic acid, glucuronic acid, and N-acetylglucosamine were found to have the following G (radicals), respectively: 3.7, 2.6, and 3.8. The EPR spectra of hyaluronic acid (at low dose) showed a doublet with hyperfine splitting of 4 to 5 gauss. Glucuronic acid after irradiation gave only a singlet which could not be further resolved. The intermediates satisfactorily account for the observed chemical degradation and EPR data. Pulse radiolysis of aqueous solutions, with 4-MeV electrons, showed that e_ aq⁻ and OH radicals react rapidly with hyaluronic acid (HA), and the following rate constants (based on disaccharide repeating unit concentration) were found: e_ aq⁻+ HA→ k₂=3 to 8× 10⁸ M⁻¹\, sec⁻¹; OH+ HA→ k₂=8± 0.4× 10⁸ M⁻¹\, sec⁻¹. The susceptibility of hyaluronic acid to radiation damage ...