Radiation Inactivation of Enzymes inside and outside Intact Cells

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Abstract
Invertase in Saccharomyces cerevesiae and cytochrome oxidase and succinic dehydrogenase in Bacillus subtilis were irradiated with electrons, deuterons and alpha particles. No differences in sensitive cross-section between the in vivo and in vitro states were found. The sensitive volumes of cytochrome oxidase and succinic dehydrogenase correspond to molecular weights of 160,000 and 310,000 respectively. Both appear to be relatively long and thin. The effect of 140,000 roentgens of X-radiation on the respiratory enzymes in B. subtilis or of 200,000 roentgens on invertase in the intact yeast cells in aqueous suspension was not measurable. It seems probable that protection against indirect radiation effects by cellular constituents is considerable.