Further studies on high molecular weight fowlpox virus DNA and its hydrodynamic properties

The intrinsic viscosity of fowlpox virus DNA measured at low shear stress in a rotating cylinder viscometer averages 447 dl/g. Calculation of the molecular weight from intrinsic viscosity data gives a value of approximately 200 × 10 6 daltons and agrees well with the molecular weight previously determined by other methods. Fowlpox DNA shows an anomalous behavior after heat denaturation with as much as 50% of the DNA exhibiting a buoyant density in CsCl similar to that of the native DNA. Denaturation in the presence of 1% formaldehyde virtually eliminates this nativelike material. Sedimentation velocity and buoyant density studies on alkaline-denatured fowlpox DNA give no evidence for covalent cross-links in the molecule. Centrifugation of denatured fowlpox DNA in an alkaline CsCl gradient revealed only one band, indicating that there is no significant difference in the guanine + thymine content of the complementary strands.