New procedure for concentration and analytical isoelectric focusing of proteins

Proteins in aqueous salt solutions (up to 4 mil) were adsorbed by hydrophobic interaction on phenyl-Sepharose gel (0.1 ml) in small columns. After washing out excess salt, gels were applied on the surface of flat bed polyacrylamide gels for isoelectric focusing, which resulted in efficient desorption and transport of protein out of the phenyl-Sepharose gel. There was no difficulty in obtaining a fifty-fold concentration. The following parameters at adsorption of protein were studied: (i) salt concentration in the protein solution; (ii) phenyl-Sepharose gel adsorptive capacity for protein; (iii) suitable volume of washing solution for the phenyl-Sepharose gel. Theoretical aspects on factors promoting adsorption and desorption of proteins on phenyl-Sepharose gel are discussed. Also discussed are earlier used procedures for concentration and/or dialysis. When dilute protein solutions are to be examined for analytical purposes, the proposed procedures seems to be a valuable aid, which does not require expensive equipment, and is quick and simple to perform.