Gel Electrophoresis in Protein and Peptide Analysis

Abstract

Gel electrophoresis is a widely used method in biochemical research; a number of different forms of gel electrophoresis have been developed and applied to the analysis of proteins and peptides. The most popular form is polyacrylamide gel electrophoresis (PAGE), in which proteins are separated within a gel matrix on the basis of differences in their charge density and/or relative molecular mass (M r ). Polyacrylamide gel is also widely used as a media for the generation of pH gradients in an isoelectrofocusing (IEF) technique, where separation of proteins is due to their differences in isoelectric point (pI). Two‐dimensional (2D) electrophoresis is an extremely powerful separation technique, allowing differentiation of proteins on the basis of their pI in IEF, and their M r in sodium dodecyl sulfate (SDS)/PAGE. Agarose gels are rarely used today in the electrophoretic analysis of proteins; their utility is mainly restricted to the immunoelectrophoretic techniques, which allow the characterization of proteins by their migration in gel and immunological properties. This article provides a brief history of gel electrophoresis and describes the principles of major electrophoretic techniques. The utility of gel electrophoresis in different fields of biochemical research is also demonstrated. Topics included are analytical and small‐scale preparative separations of complex proteins samples; determination of molecular mass of the electrophoretically separated proteins and polypeptides; electrophoretic micropreparation of a protein sample for its further immunochemical, enzymatic, and chemical analysis; study of protein interactions with different ligands; examination of protein unfolding and its quaternary structure. The advantages and limitations of the described techniques are discussed.