Quantum Yields for Inactivation of Tobacco Mosaic Virus Nucleic Acid by Ultraviolet Radiation (254 nm.)

The quantum yield, under non-photoreactivating conditions, for inactivation of tobacco mosaic virus RNA by ultraviolet radiation (254 nm.) is independent of the RNA concentration but varies appreciably with the ionic strength of the irradiation solvent, being approximately three times greater in water than in 0.1 m-potassium phosphate buffer. Photoreactivation of inactivated tobacco mosaic virus RNA is dependent on RNA concentration, ionic strength of solutions during irradiation, and on the light quality used for photoreactivation. These data can be interpreted as evidence that pyrimidine hydrate is a lethal lesion at least in RNA irradiated at low ionic strength.