Molecular weights of coliphages and coliphage DNA: II. Measurement of diffusion coefficients using optical mixing spectroscopy, and measurement of sedimentation coefficients

The molecular weights of the coliphages T4, T5 and T7 have been determined by measurement of their diffusion coefficient (D) and sedimentation coefficients (S). D was determined using the new technique of optical mixing spectroscopy. Values of D20,w for T4, T5, T7, and λ phages were found to be (in units of 10−7 cm2/sec) 0.295 ± 0.003, 0.397 ± 0.004, 0.603 ± 0.006, and 0.497 ± 0.005 respectively. Values of S20,w0 were found to be (in Svedbergs) 890 ± 15, 615 ± 10, 453 ± 8, and 360 ± 10, respectively. Using values of \̄gn from the preceding paper Bancroft & Freifelder (1970) the phage molecular weights for T4, T5, and T7 were then calculated to be (in millions) 192.5 ± 6.6, 109.2 ± 4.0, and 50.4 ± 1.8. From the percentage DNA in these phages (Bancroft & Freifelder, 1970) the molecular weights of T4, T5, and T7 DNA were found to be (in millions) 105.7 ± 3.8, 67.3 ± 3.1, and 25.8 ± 1.0.