Translational and rotational diffusion of tobacco mosaic virus from polarized and depolarized light scattering

The translational and rotational dynamics of tobacco mosaic virus in sodium phosphate buffer (pH =7.5) solutions has been investigated by polarized and depolarized light scattering Rayleigh linewidth studies. For concentrations ranging from 1.75 × 10 −4 g ml −1 to 0.25 × 10 −4 g ml −1 the translational diffusion coefficient (D T ) has been found to be slightly concentration dependent and extrapolation to zero concentration gives D 0 20°C = 0.34 ± 0.01 × 10 −7 cm 2 S −1 . A full analysis of the polarized spectra obtained at high and low scattering angles and the depolarized spectra at near zero scattering angles has enabled these techniques to be compared and the rotational diffusion constant D R to be determined. At a solution concentration of 1.75 × 10 −4 g ml −1 a mean value is found to be D R 20°C = 350 ± 30s −1 . These values of D T and D R are in approximate agreement with calculations based on models of the tobacco mosaic virus molecule as a cylindrical rod.