Affinity ultrafiltration of proteins

Affinity ultrafiltration combines high-volume processing capability of memb rane filtration with high selectivity, which can be achieved in affinity me thods of protein purification. This technique is based on the principle tha t when a protein to be purified is free :in solution, it passes through the ultrafiltration membrane, whereas when it is bound to a macromolecular aff inity ligand placed on one side of the membrane, it is constrained to that side of the membrane. Compounds which do not bind to the ligand pass freely through the membrane and are thus separated from the protein-ligand comple x. After all the undesired components have been removed, the protein is des orbed from the ligand by addition of an appropriate dissociating medium and then recovered in the filtrate. The review describes basic principles and characteristics of the method. In addition, some applications of affinity u ltrafiltration for protein purification are given.