Application of free-solution capillary electrophoresis to the analytical scale separation of proteins and peptides.

The application of free solution capillary electrophoresis (FSCE) to the separation of protein and peptide mixtures is presented. Both qualitative and quantitative aspects of FSCE separations are considered. In addition, a brief introduction describing the separation principle behind FSCE separations and a discussion of electrophoretic mobility are included. The applications were chosen in order to highlight the selectivity of FSCE separations and to demonstrate applications of potential practical interest to the bioanalytical chemist. Comparison of FSCE relative to traditional analytical separation alternatives is stressed throughout. The examples are presented in three broad categories: protein separations, peptide separations, and the application of both to the analysis of recombinant protein products. In the first section, FSCE separations of peptide mixtures are presented which demonstrate the suitability of FSCE for the analysis of the purity of peptide samples, the homogeneity of peptide samples prior to sequencing, the identity of peptides by using electrophoretic mobility values, and the reduction of an intrachain disulfide bridge. In the second section, protein separations are presented that show the resolution of glycoproteins having the same primary structure and the separation of immune complexes from free unreacted antibody and antigen. In the final section, highly purified and well-characterized samples of biosynthetic human insulin (BHI), biosynthetic human growth hormone (hGH), and their derivatives were used to evaluate FSCE as a complement and/or alternative to conventional analytical separation techniques for the determination of purity and identity of biosynthetic human proteins. In addition, the quantitative aspects of FSCE analysis such as linearity of response, precision, and limit of detection were examined.