Protein transport through porous membranes: Effects of colloidal interactions

Traditional analyses of membrane transport have generally considered only steric (size-based) interactions between the solute and pores. Recent experimental work has clearly demonstrated the importance of longer-range colloidal interactions on the rate of solute transport. These interactions can dramatically affect membrane performance, changing the membrane from being almost completely permeable to completely retentive for a given solute. This manuscript discusses several applications of colloidal interaction theory to membrane systems, highlighting the tremendous insights that have been obtained into the performance of real membrane systems as well as the limitations of available theoretical descriptions. New calculations are presented for the transport of charged solutes through porous membranes which explicitly account for the effects of charge regulation arising from the dissociation of specific ionizable surface groups. The importance of non- equilibrium phenomena in membrane systems is also examined. Particular emphasis is placed on the use of membrane systems for protein separations, including the importance of protein structure and biochemistry on membrane selectivity.