Effects of Certain Metal Salts on the Inactivation of Solid Trypsin by Ionizing Radiation

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Abstract
Copper and iron sulfates, when present in the solid enzyme, increase the inactivation dose considerably; but cobalt, thallous, and cerous sulfates are ineffective. Zinc sulfate has a small protective action. Copper and iron sulfates form complexes with trypsin which can be detected by their optical absorption, and the maximum complex formation occurs at about the concentration which gives the maximum protective effect. Cobalt sulfate does not form a complex detectable in this way. The samples of trypsin used in this investigation are oxygen sensitive with D vac D air about 2 for pulsed electrons. As added cysteine has little effect on the inactivation doses, it appears that these samples already contain a protective agent, which, however, is not readily removed. The effect of oxygen on the samples containing copper and iron is somewhat less than on the original trypsin; with the other metal salts, the effect of oxygen is the same as on trypsin alone. There appear to be two types of protective action, in which (a) the effect of oxygen is not greatly different from its effect when the agent is absent (metal ions); (b) the effect of oxygen is enhanced by the protective agent (e. g., cysteine). Mechanisms of these processes are discussed.

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