Abstract
The buoyant density of particles of maize dwarf mosaic virus (MDMV) in CsCl was influenced by pH and divalent anion concentration. Particle density increased with increasing pH at low buffer molarity; it decreased with increasing divalent anion concentration. The density shifts induced by divalent anions and acid pH were reversible, but those occurring at alkaline pH were irreversible. Of the strains examined, all behaved identically except 13B (MDMV-B), which was denser under all conditions and so could be physically separated from MDMV-A.