Minor components associated with turnip yellow mosaic virus

Preparations of turnip yellow mosaic virus purified by differential centrifugation contain three classes of nucleoproteins in addition to the infectious virus particles. Two of these minor components have a higher buoyant density in CsCl and higher sedimentation coefficient than virus particles. They contain degraded (low S) viral RNA and are not significantly labeled when infected leaves are pulsed with ³²P. They appear to be degradation products of the virus particle whose physical properties are attributable in part to increased binding of cations. The error in the molecular weight of TYMV determined by light-scattering, due to maximal contamination with these minor components, was evaluated quantitatively and found to be negligible.