IN ACTIVATION OF A STRAIN OF TOBACCO NECROSIS VIRUS AND OF THE RNA ISOLATED FROM IT, BY ULTRAVIOLET RADIATION OF DIFFERENT WAVE‐LENGTHS

Abstract— A train of tobacco necrosis virus (TNV) and infective nucleic acid isolated from it (TNV‐RNA) are equally susceptible to inactivation by U.V. radiation at all wave‐lengths tested (230‐290 m_μ) and can be photoreactivated to the same extent by exposing inoculated host plants to daylight. The shape of the action spectrum for inactivation by U.V. of TNV and of TNV‐RNA follows that of the absorption spectrum of TNV‐RNA. Thus, unlike the RNA of tobacco mosaic virus, the RNA of TNV behaves in all these respects in the same way irrespective of whether it is inside or outside the virus particle. To inactivate TNV or TNV‐RNA to 50 per cent of their original infectivities, each mg of RNA must absorb about 0.27 joules of radiation energy of any wave‐length between 230 and 290 mp, which corresponds to a quantum yield of about 0.65 ×10^‐3 at 260 mμ.