Abstract
Tobacco mosaic virus can be labelled with P32during homogenization of the diseased tissue with a soluble, stable, unknown phosphate compound. The label remains associated with the virus during purification and can be isolated from the virus by incubation in potassium hydroxide. The labelled phosphate compounds released are mainly adenylic, cytidylic, uridylic, and guanylic acids. The addition of p-fluoro-DL-phenylalanine and 2-thiouracil reduces the amount of P32found in the virus. Chloramphenicol does not inhibit P32incorporation into TMV.