Direct determination of native proteins in miniaturized capillary electrophoresis system

Lysozyme (14.4 kDa), BSA (66.4 kDa) and beta-galactosidase (116 kDa) were successfully separated and determined directly within 80 seconds using a laboratory-made miniaturized capillary electrophoresis apparatus provided with a confocal fluorescence spectrometry. Several parameters controlling on the detection limits, including focusing effect, laser power and buffer composition were tested and optimized. Separation buffer was 10 mM phosphate containing 4 mM CTAB at pH 2.5. The LOD values for lysozyme, beta-galactosidase and BSA were found as 9.0, 13.0 and 55 fg/microl, respectively. This miniaturized CE system offers a lot of advantages for protein analysis. First; it provides reproducible separation reducing wall-adsorption effects at low pH. Second, the analysis time observed from our system is in the range of chip electrophoresis applications. And finally, LOD values for standard proteins are much more lower than that of obtained from traditional gel electrophoresis method.