THE EFFECT OF HYDRODYNAMIC SHEAR ON THE DEOXYRIBONUCLEIC ACID FROM T 2 AND T 4 BACTERIOPHAGES

Abstract

In 1956, Levinthall reported autoradiographic studies of T2 and T4 bacteriophage deoxyribonucleic acid (DNA). He found that the DNA in each phage particle was present in the form of several chains, one of molecular weight about 45 X 106 and six or more of molecular weight about 12 X 106. Attempts to differentiate the large and the small pieces of phage DNA by ultracentrifugation have been unsuccessful. For example, in sedimentation velocity experiments Fleischman2 found a single peak with a sedimentation coefficient of 30 to 35 S(vedbergs) (the lower value was found on deproteinized preparations); Meselson, Stahl, and Vinograd3 reported the DNA to band with a Gaussian distribution, implying a uniform molecular weight, in equilibrium experiments in a cesium chloride gradient. With the ultraviolet absorption system in the Spinco Model E ultracentrifuge, DNA solutions below 0.001 per cent concentration can be studied, and sedimenta-tion coefficients ranging from 8-50 S have been reported.4 5 Calculating from the formula which Doty, McGill, and Rice6 derived from studies on calf thymus DNA, the large and the small pieces of phage DNA could have sedimentation coefficients about 42 and 26 S. These values may not be accurate since they are deduced from an unwarranted extrapolation of the formula, and, moreover, recent studies have