LYSOZYME FRAGMENTATION INDUCED BY GAMMA-RADIOLYSIS

Irradiation of lysozyme in frozen states in the absence of oxygen indu ces specific fragmentation at defined sites along the backbone chain. This paper localizes radio-fragmentation sites by two methods. First, N-terminal sequencing of radiolysis fragments after separation by SDS- polyacrylamide gel electrophoresis and estimation of their molecular m asses. Secondly, after purification of radiolysis fragments by reverse phase-HPLC and determination of their molecular mass by electro-spray -ionization mass-spectrometric analysis, combined to N-terminal sequen cing and total amino acid analysis. Evidence for the breakage of the p eptide bond itself (CO-NH) is given, with radio-fragmentation sites mo stly found at the surface of irradiated lysozyme in solvent exposed lo ops and turns.