Structural properties of adenovirus DNA's

Abstract

Studies of the change of the sedimentation coefficient of adenovirus type 5 DNA as a function of pH and ionic strength indicates that the DNA consisted of double-helical, linear molecules which readily denatured in alkaline solvents yielding single-stranded DNA. The DNA's of the oncogenic types 12 and 18 were found to have a similar structure, confirming the results of Green et al. 1. After heat denaturation in the presence of 12% formaldehyde, however, only a small proportion of the molecules was converted to single-stranded DNA. The resistance to strand separation possibly was due to cross-links induced by formaldehyde which were formed during denaturation in heat resistant, GC-rich sequences. DNA which was liberated from purified particles of adenovirus type 5 by treatment with sodium dodecyl sulfate or alkali occurred as more or less compact, reticular structures as observed by electron microscopy. Evidence suggested that the molecules were kept in this form by a protein which remained associated with the DNA. The molecular weight of type 5 DNA was calculated from the values of s° 20,w and the intrinsic viscosity [η], using the Mandelkern-Flory equation 2. A molecular weight of 23.4·10 6 or 24.9·10 6 was found, depending on the β value used. Molecular weights of native and denatured DNA of types 5, 12 and 18 were calculated, using the equations of Studier 3. It was found that the values of the DNA's of the oncogenic types 12 and 18 were slightly lower than the values of the nononcogenic type 5.