Inactivation of Infectious Nucleic Acid from Tobacco Mosaic Virus by Ultraviolet Light (2537 A)

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Abstract
The quantum yield for the inactivation of tobacco mosaic virus (TMV) is very low as compared with typical proteins. Considering the size of the virus, however, it is remarkable that the yield is as high as it is and it has been suggested that the nucleic acid in the virus may have a greater sensitivity to UV than would a biochemically active protein molecule of the same size (Bawden and Kleczkowski, 1955). The infectious nucleic acid (RNA) from common TMV (Schuster, Schramm and Zillig, 1956) is about 6 times as sensitive to inactivation by UV as it is in the form of intact virus. Inactivation takes place, by a "one-hit" process at pH 7.3 in 0.02 [image] phosphate buffer, without a reduction in intrinsic viscosity (210 - 280) at 6[degree], but with a slight reduction in optical density at 2600A (less than 1%). It is clear that inactivation involves only a local change on the RNA chain. The energies required for 50% inactivation of the following substances in joules per mg are nucleic acid (free), 0.43; nucleic acid (in the intact TMV, calculated), 2.7; TMV, 0.15; enzymes and antibodies, 0.75.