Hydrodynamic Properties of Rigid Complex Molecules

Abstract

Three hydrodynamic properties–the translational frictional coefficient, the rotational frictional coefficient, and the intrinsic viscosity–for a model molecule composed of different frictional elements in an arbitrary conformation are calculated by a tensor method. The method adopts the Oseen tensor rigorously and differs from Kirkwood’s in the respect that the present method is a unified one for a rigid molecule, but gives the same result for the translational frictional coefficient. The method is extended to Bloomfield’s “shell model”. In the case of a sphere, the present method gives the Stokes–Kirchhoff law for the rotational frictional coefficient and the Einstein relation for the intrinsic viscosity. The present theory agrees well with experiments. For bovine serum albumin, the hydrodynamic properties are more sensitive to the difference of molecular structures in the order, the translational frictional coefficient, the intrinsic viscosity, and the rotational frictional coefficient. For γ globulin, the Edelman–Gally model is shown to be consistent with the hydrodynamic properties at various stages of degradation.