Notes on the Derivation of Sedimentation Equilibrium Equations

Abstract

In the traditional kinetic approach as often taught in physical chemistry courses, sedimentation equilibrium of a macromolecular solution in the ultracentrifuge cell is pictured as the state in which forward transport of a macromolecular solute by centrifugal force is exactly counterbalanced by backward diffusion transport of the same solute by its chemical potential gradient at any point in the solution column. For the formulation of sedimentation equilibrium of solutions containing more than one solute, however, this approach is of no use and has to be replaced by the one based on the thermodynamics of multicomponent systems (Fujita, 1975). Such formulation was initiated by Goldberg (1953), discussed by many authors, and finally almost completed by Casassa and Eisenberg (1964). Actually, there are few that can be added to their elegant theory, but many workers may not find simple to follow its sophisticated mathematical content.