X-ray Inactivation of Lysozyme in Dilute Solution

Summary

The inactivation of lysozyme was measured in the following conditions: 40–500 µg/ml. in 0·05 M phosphate buffer, pH 6–7, 0°c, in the presence of air. The activity decreased linearly with the dose to < 25 per cent residual activity. The yield was 0·18 molecules/(100 eV). p-Aminobenzoic acid, cysteine and phenylalanine have a protective action, which parallels their rates of reaction with (OH·) radicals; this indicates that (OH·) is primarily responsible for inactivation of the enzyme. The meaning of the activity-dose relationship and the value of the yield are discussed.