ULTRACENTRIFUGAL FRACTIONATION AND IRON DISTRIBUTION IN INFECTIOUS NUCLEATES FROM TOBACCO MOSAIC VIRUS

Abstract

A new ultracentrifugation technique, namely the use of an immobilizing carborundum bed, is described for the fractionation of sedimentable but highly diffusable materials. More highly infectious, sedimentable, nucleate component in preparations were obtained by treating tobacco mosaic virus with sodium dodecyl sulfate or phenol. As the infectivity of the highly active component in the sediment fraction soon decreases and that of the lowly active component in the supernatant liquid increases to about the original level when the infective solutions are allowed to stand, the concentration of the more highly infectious component appears to be the result of a dynamic equilibrium between infectious and noninfectious nucleate components. Radioactive iron, Fe59, was incorporated into the virus during its rapid synthesis in newly infected Turkish tobacco plants in about 25 times the quantity found when the same amount of radio-active iron was administered to fully infected plants. When the radio-active virus was treated with phenol for the preparation of the nucleate fraction, about 95% of the Fe59 was removed together with the protein in the phenol extracts. When the radioactive nucleate fraction was subject to ultracentrifugation in the presence of an immobilizing carborundum bed, iron was concentrated in the more highly infectious sediment in roughly the same ratio as the increase in infectivity.