Measurement of protein charge and ion binding using capillary electrophoresis

A new technique is described for the rapid and accurate measurement of electrophoretic mobilities of proteins in different solution environments using capillary electrophoresis. Data were obtained at different pH using surface-modified capillaries to reduce nonspecific protein adsorption and using hydrodynamic mobilization to improve reproducibility and overall accuracy. The net protein charge and extent of anion binding were evaluated from the mobility data obtained in different pH and ionic environments for bovine serum albumin. The results were in good agreement with titration data obtained using ion-selective electrodes and mobility data obtained using free solution electrophoresis. The method requires extremely small amounts of protein (picogram quantities and nanoliter volumes) and is easily automated, making it very suitable for protein characterization and for initial screening of possible separation techniques.