Affinity ultrafiltration can provide high resolution separations by exploiting the selectivity of biomolecular binding interactions while maintaining the high throughput characteristic of conventional ultrafiltration processes. Mattiasson and Ramstrop (1984) demonstrated the feasibility of using affinity ultrafiltration for the purification of Concanavalin A using heat killed Saccharomyces cerevisae as the affinity ligand (Mattiasson and Ramstrop, 1984). The separation was performed using membranes with a molecular weight of 1,000 Kd which were fully retentive to the very large binding complex formed between Concanavalin A and the S. cerevisiae while allowing unbound species to pass relatively freely through the membrane. Subsequent studies have examined the isolation of urokinase using N-acryloyl-maminobenzamide copolymerized with acrylamide as an affinity macroligand (Male et al., 1990) and the purification of avidin using biotinylated liposomes (Powers et al., 1990) among others. Affinity ultrafiltration has also been used to separate chiral molecules using stereoselective macroligands. For example, BSA has been used for the optical resolution of racemic mixtures of tryptophan (Poncet al., 1997) and HSA for ibuprofen (Itoh et al., 1997).
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