Hard quasispherical particle models for the viscosity of solutions of protein mixtures.

Recently reported measurements of the viscosity of three monoclonal antibodies, their binary mixtures, and a binary mixture of an antibody and albumin over a broad range of compositions (Galush et al., J. Pharm. Sci. 2011,101, 1012) were quantitatively accounted for to within experimental uncertainty by an extension of the hard quasispherical particle model suggested by Ross and Minton (Biochem. Biophys. Res. Commun. 1977, 76, 971) and by a generalization of the hard sphere equation of Krieger and Dougherty (Trans. Soc. Rheol. 1959, 3, 137) . Further generalization of these equations to treat the concentration-dependent viscosity of self-associating proteins is suggested.