Abstract
Cowpea chlorotic mottle virus (CCMV) sediments as a single species but is heterogeneous when centrifuged in CsCl. The heterogeneity is not due to degradation. The original interpretation of the nucleoprotein distribution in CsCl was based on the assumption that two populations of particles of equal densities but different diffusion rates formed in CsCl, the more diffuse band being composed of monomers and the less of tetramers (Bancroft et al. 1968). However, in light of the recently demonstrated behaviour of CCMV-RNA in polyacrylamide gels (Fowlks & Young, 1970; Bancroft, 1971) and the correlation between band density and RNA size found by Lane & Kaesberg (1971) for brome mosaic virus which has a similar RNA distribution to that of CCMV, a reconsideration of the explanation for the behaviour of CCMV in CsCl was thought to be appropriate and is now presented.
CCMV was grown, purified and assayed as described (Bancroft et al. 1968).