X-ray small-angle studies of dimensions and weight parameters of T2, S_D and DD2 bacteriophages

Bacteriophages T2, S_D and DD2 have been studied in solution by the X-ray small-angle technique over a wide range of concentrations. The measurements were made on an absolute scale. Several distinct subsidiary maxima on the scattering curve have been observed for all three phages. Some models of investigated bacteriophages are suggested and the calculated small-angle curves for them compared with the experimental curves. Good agreement is achieved for the `best' models. For T2 the best model is more elongated than it appears from electron micrographs. The weight of the bacteriophages was determined from the absolute intensity measurements: 4.2; 1.8; 1.1 x 10-1 g for T2, S_D and DD2 respectively. From these data and the chemical compositions of the phages the molecular weight of phage DNA is calculated. Furthermore the volumes and hydrations of all phages are determined. Some measurements with phage So were made in a solution with higher electron density and the size of the DNA core was estimated. It was established that the hydration of DNA is higher than the hydration of the protein shell. Some wide-angle X-ray patterns were obtained with S_D solutions and gels. From these data it followed that the conformation of DNA in native phage particles is close to the B-form.