Usefulness of SEPARAX-SPTM membrane for supporting medium in cellulose acetate membrane isoelectric focusing

SEPARAX-SP membrane is used generally as supporting medium for serum protein fractionation in many clinical laboratories, but it has not been used for isoelectric focusing (IEF). Although the exclusive cellulose acetate membrane for IEF is a SEPARAX-EF membrane, we studied usefulness of SEPARAX-SP membrane as supporting medium for cellulose acetate membrane IEF as comparison with SEPARAX-EF membrane. Serum sample was applied and electrophoresed in according to our method. After electrophoresis, all cellulose acetate membranes were stained with Coomassie brilliant blue G-250. The both membranes showed clear and similar isoelectrophoretic patterns of serum protein. Furthermore, we confirmed that isoelectric focusing can be carried out on six layers of SEPARAX-SP membranes as same as SEPARAX-EF membrane. All six SEPARAX-SP membranes were showed clear isoelectrophoretic patterns of serum protein, but detected serum protein concentration was decreased in lower layers of SEPARAX-SP membrane. Therefore, we examined the distribution of protein among the six layers of SEPARAX-SP membrane and compared to those of SEPARAX-EF membrane. The ratio of protein distribution between top membrane and bottom membrane was 2:1 on SEPARAX-SP membrane against to the ratio of 30:1 on SEPARAX-EF membrane. Furthermore, protein distribution of six layers on SEPARAX-SP membrane was more uniform than that on SEPARAX-EF membrane. These results indicated that SEPARAX-SP membrane was useful supporting medium for cellulose acetate membrane IEF.