Printed in Great Britain 427 Purification and Fractionation of Alfalfa Mosaic Virus

Preparations of alfalfa mosaic virus made by precipitation with poly-ethylene glycol were as infective and contained the same relative proportions of components a virus preparations made by ultracentrifugation. A column chromatographic procedure using a continuously decreasing concentration gradient of polyethylene glycol was employed to fractionate he nucleoprotein components of the virus. By this procedure a partial sorting of the virus components into three groups according to particle length was achieved. Particles in the three groups are thought to correspond to top component a, top component b,and a mixture of middle and bottom components