High-performance capillary electrophoresis of hydrophobic membrane proteins

Hydrophobic membrane proteins, extrinsic and intrinsic ones, were separated by high-performance capillary zone electrophoresis (HPCZE) and high-performance capillary isotachophoresis (HPCITP). In the case of HPCZE with both coated and uncoated quartz capillaries the addition of 7 M urea to the separation buffers was necessary to achieve reproducible results. In the HPCITP experiments PTFE capillaries were used. When spacers were used, e.g., ampholytes, additional splitting of peaks was observed. The splitting was caused by the microheterogeneity of the investigated proteins, which are differently glycosylated and/or phosphorylated.