Preparative isoelectric focusing of proteins on slabs of polyacrylamide gel

Abstract

An isoelectric focusing technique on a mg-preparative scale using polyacrylamide gel slabs (IFPA) is described. IFPA is carried out on glass plates coated with gel layers up to 4 mm thick. The maximal load capacity for protein mixtures is about 40 mg or 1 mg/protein band/cm 2 of gel. Focusing runs are performed in a simple plastic-coated aluminum apparatus in a refrigerator without additional forms of cooling. Colorless proteins are localized by Coomassie Brillant blue staining of small gel stripes from both edges or by densitometric tracing at 280 nm on quartz plates. Using this technique, the isolation of five biologically active isohormones of human chorionic gonadotropins (hCG) was possible.