Biochemical, biophysical, and biological properties of densonucleosis virus (paravovirus). II. Two types of infectious virions.

Among the infectious densonucleosis virus (DNV) particles, two types of virions, DNV-I and DNV-II, have been identified. The density of DNV-I was about 1.40 g/ml and depended on the pH, whereas the density of DNV-II was independent of the pH and was 1.44 g/ml. The sedimentation rates of these particles were 111S and 89S, respectively. The specific extinction coefficients and the absorption spectra, corrected for light scattering, were also different for these two types. The electrophoretic mobility of both types of virions was identical under the experimental conditions used. Both types of particles contained single-stranded DNA with similar physicochemical properties. The difference between these types of virions seemed to be due to a different protein content, DNV-II containing about 600,000 daltons less protein, and to a different quaternary structure as indicated by the change in the density of DNV-II, in the presence of divalent cations, without any change in the density of DNV-I.