Boundary Problems in the Sedimentation and Electrophoresis of Complex Systems in Rapid Reversible Equilibrium

Abstract

MANY problems of current interest, for example, the dissociation of nucleoproteins, the reaction of antigens with antibodies, and the combination of proteolytic enzymes with inhibitors, to mention only a few, are at first sight open to attack by the conventional methods of sedimentation and electrophoresis. To a greater or less extent, however, in all these instances, instead of the underlying process of differential transport leading to a simple resolution of the components at the boundaries between solution and solvent, the situation is confused by re-equilibration as the reactants and products tend to be separated from one another. This effect has been much discussed^1–3, but an exact theoretical treatment of the general case seems to be prohibitively difficult if all factors, including the finite rate of approach to equilibrium and the simultaneous spread of the boundaries through diffusion, are taken into account. Even so, Ogston and Field³ have calculated the form of the sedimentation boundary by numerical methods for the particular case of the dissociation of human hæmoglobin.