INFLUENCE OF THE SIZE OF THE POLAR HEAD OF NONIONIC DETERGENTS ON MEMBRANE-PROTEINS IMMUNOAFFINITY PURIFICATION

Nonionic polyoxyethylene type detergents (C(x)E(y)) are widely used to solubilize and purify membrane proteins. The detergent hydrophobic mo iety (C-x) replaces phospholipids at exposed hydrophobic regions of th e membrane proteins. During chromatography on an immobilized anti-Kell antibody to purify Kell protein (an integral erythrocyte protein), it was observed that the size of the polar head of an non ionic detergen t added to the mobile phase appeared to influence the interaction of t he detergent-protein complex with the immobilized antibody. Further st udies were performed using another erythrocyte membrane protein, Glyco phorin C and three anti-GPC monoclonal antibodies directed against thr ee epitopes of the extracytoplasmic domain of the protein. The interac tion of GPC with the three Protein A-coupled monoclonal antibodies was studied in the presence of three detergents C(12)E([9]), C(13)E([15]) and C(12)E([23]). It was observed in batch mode and in column chromat ography experiments that the adsorption of GPC to the immunoaffinity s upports decreased as the size of the detergent polar head increased. T hus, the polyoxyethylene chain of a detergent might prevent the intera ction of the detergent-protein complex with the immobilized antibody.