Distribution of Radiocarbon in Tobacco Mosaic Virus

Abstract

WE have made radioactive tobacco mosaic virus by exposing leaves from infected tobacco plants to radioactive carbon dioxide for one day in light, treating the homogenized leaves with buffer solution, and purifying the virus by repeated precipitation at the isoelectric point¹. The virus is determined by colour reaction, burned, and the radioactivity of the resulting carbon dioxide measured with a gas Geiger counter². It has been found that the specific radioactivity (activity per unit weight) of the virus decreases with increasing ‘age’, that is, with increasing time-interval between infection and radiophotosynthesis, up to an age of about four weeks^3,4. In addition, one sample of tobacco mosaic virus, aged two months, was analysed for distribution of radioactivity. The nucleic acid was split off by treatment with trichloroacetic acid⁵, and the protein hydrolysed and divided into the individual amino-acids by column chromato-graphy⁶. A large part of the radiocarbon was found in the nucleic acid, and the distribution of the radiocarbon among the individual amino-acids was quite uneven⁷.