The physical properties of DNA from T2 and T4 bacteriophage

Abstract

The project was designed to provide a molecular characterization of the DNA of the T-even bacteriophages, T2 and T4. It also attempted to clarify the problem of a possible bipartite distribution suggested by autoradiographic experiments. The phage were grown on E. coli strain B in synthetic glycerol medium. Highly purified phage stocks were obtained by premature lysis and centrifugation. DNA was released from the phage by osmotic shock and cadmium cyanide-lysine treatment. The DNA solutions were deproteinized (except for whole shockates) by treatment with chloroform-amyl alcohol. Sedimentation studies on purified DNA preparations revealed a single, fairly sharp boundary with a median sedimentation coefficient of 30 s. The intrinsic viscosity was 114 dl./g. The molecular weights determined by light scattering and by density gradient centrifugation were 14 × 10 6 and 11 × 10 6 respectively. These values are within the range expected for DNA with the above sedimentation coefficient and intrinsic viscosity. The molecular weight distribution calculated from the sedimentation boundary was found to be much narrower than a Flory (most probable) distribution. An analysis of the sedimentation patterns of whole shockates revealed no evidence for a discrete, large component as suggested by the autoradiograph experiments. A subsequent investigation (Davison, 1959) suggests that the use of a syringe in sedimentation studies may degrade large molecules of DNA. The relationship between the 30 s DNA and that existing within the phage may therefore be uncertain.