The effect of hydrodynamics on the diffusivity of charged macromolecules: Application to BSA

Using the Batchelor/Felderhof hydrodynamic perturbation of the friction factor in the Stokes–Einstein expression for the diffusion coefficient, we have calculated the correction to the latter due to electrostatic interactions between charged spherical particles in a solution of low ionic strength. We obtain an excellent agreement between this theory and the early experimental results of Doherty and Benedek using BSA. Our theoretical fits to the BSA diffusivity data show a substantial improvement over the recent theoretical predictions of Schor and Serrallach, who considered only the thermodynamic (and not the hydrodynamic) corrections to the diffusion coefficient.