Purification of large proteins using ion-exchange membranes

Experimental characterization of a standard, commercially available ion-exc hange membrane cartridge for purification of large protein molecules was ca rried out. Individual membranes within the cartridge was qualitatively anal yzed for possible defects in morphology and/or sorption patterns. Analysis was based on observation of membrane morphology using scanning electron mic rographs (SEM) and protein binding patterns using dye-binding experiments. SEMs show polydispersity in pore size distribution that is substantiated by non-uniform protein binding patterns in equilibrium adsorption. Adsorption under dynamic conditions showed dependence of binding on order of membrane in the cartridge, face of the membrane and flow rate of the experiment. Th ese experimental findings point toward limitations involved in using ion-ex change membranes for purification of large proteins. Furthermore, these exp eriments also magnify limitations in current theoretical understanding of m embrane separations. (C) 2001 Elsevier Science Ltd. All rights reserved.