The Behaviour of Some Isometric Plant Viruses Heated in vitro as determined by Particle Stabilizing Forces

Absorbance-temperature profiles, at 400 nm, of plant viruses with one or more kinds of isometric particle, were determined. Two temperatures were determined, Td (the temperature at which E 400 begins to increase) and Tf (the temperature at the inflexion point of the curve). The behaviour on heating at these temperatures was of two main types. Heating in vitro appears to be a useful means of making a gross subdivision of isometric plant viruses into two groups typified by cucumber mosaic virus and turnip yellow mosaic virus, respectively, in agreement with Kaper's (1971a) suggestion.