CONTRASTING OXYGEN-EFFECTS IN THE INACTIVATION OF RIBONUCLEASE-A BY N.3,(SCN).-2 AND .OH RADICALS

N3{dot operator} exhibits higher efficiency than{dot operator}OH in the inactivation of RNase in de-acerated (neutral) aqueous solution. In O2-saturated solution the{dot operator}OH-induced inactivation is enhanced, but N3{dot operator} and (SCN)2{dot operator}- become remarkably inefficient. Our results suggest that semi-oxidized tyrosine, the predominant initial defect induced by N3{dot operator} and (SCN)2{dot operator}- but not by{dot operator}OH, can be re-reduced upon reaction with O2{dot operator}- or cysteine. © 1979 Springer-Verlag.