Automated Ferguson analysis of glycoproteins by capillary electrophoresis using a replaceable sieving matrix

Obtaining accurate molecular weight estimates for glycoproteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) has been difficult due to the lack of SDS binding by the carbohydrate moieties of the proteins. This leads to lower charge-to-mass ratios for SDS-glycoprotein complexes, resulting in over-estimation of molecular weights by SDS-PAGE. In order to minimize these inaccuracies for proteins with abnormal charge-to-mass ratios, a Ferguson plot may be employed. This application requires the determination of relative mobilities for standard proteins in addition to unknowns at several different gel concentrations. Historically, this technique has not been popular because it requires time-consuming preparation of gels with varying matrix concentrations, electrophoresis, and staining/destaining of gels. In this paper a procedure is demonstrated which automatically generates all of the data required for a Ferguson plot using a replaceable sieving matrix (thereby eliminating gel polymerization) in a capillary format. In addition, this technique possesses the advantages inherent to capillary electrophoresis, namely, very fast separation times, and on-line monitoring which allows quantitation and precludes post-separation staining and destaining of gels.