Radiation Damage and Free Radical Production in Irradiated Ribonuclease

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Abstract
The effect of gaseous environment on the radiation sensitivity of dry ribonuclease was examined. An enhancement of the anoxic sensitivity by a factor of 22 was observed for irradiation in oxygen. Exposure of the enzyme to oxygen following irradiation under anoxic conditions results in a 1.5 times increase in the sensitivity. A nitric oxide environment protected the enzyme, reducing the sensitivity to .61 of the anoxic value. Stable free radicals were produced in the enzyme by the irradiation and were observed in an electron spin resonance spectrometer. Changes in spectrum were observed in every treatment which resulted in a change in the sensitivity. This suggests that a correlation exists between the stable free radicals, and the alteration of the activity of the enzyme.