Nonequilibrium thermodynamics of membrane-confined electrophoresis.

Membrane-confined electrophoresis (MCE) is an electrophoretic transport method in which macromolecules in solution are confined within a cuvette through which a current flows. Small ions that can permeate the membranes permit current flow. The method is the electrophoretic analog to analytical ultracentrifugation. Systems in the MCE instrument are described by nonequilibrium thermodynamics. This description forms the basis of a program, implemented using finite element methods, that can model transport processes in such systems over an extended time, from arbitrary starting conditions to steady state. Issues relevant to the analysis of systems in which macromolecular species are involved in mass-action associations are discussed. Particular attention is given to steady-state electrophoresis, from which measurements of reduced molecular charge are sought. The relationship of such measurements to valence is discussed.