Dynamic light scattering of the bacteriophage T4B: determination of translational diffusion coefficients and centres of rotation

Using dynamic light scattering, the translational diffusion coefficient (D_T) and the distance between the hydrodynamic centre and the centre of the head (r₀) of the bacteriophage T4B have been determined. For a particle with retracted tail fibres we found D_T20.w =2.88 (2.88 ± 0.02) × 10^?8cm²s^?1 and r₀ = 52 ± 1 nm. For a phage with fully extended tail fibres D_T20w = (.210 ± 0.02) × 10^?8cm²s^?1 and r₀ = 112 ± nm. These data were obtained by interpreting the correlation function using a theory which takes into account the influence of the lollipop shape of the phage. In the literature this influence has not been taken into account, which has led to erroneous values of diffusion coefficients for T4B and other phages. The sedimentation coefficient of T4B phage is 1040 ± 5 S (fibres retracted) or 829 ± 4 S (fibres extended). With the above mentioned diffusion coefficients, these values correspond to a molecular weight of 236 × 10⁶ ± 3 × 10⁶. Finally, the theory used in this study is applied to other bacterial viruses, to correct reported values of the translational diffusion coefficients and of the corresponding molecular weights of these viruses.