Recent Advances in Capillary Isoelectric Focusing

Capillary isoelectric focusing (cIEF) combines the high resolving power of conventional gel isolectric focusing with advantages of capillary electrophoresis (CE) instrumentation. As in gel IEF, proteins are separated according to their isoelectric points (pIs) in a stable pH gradient formed by ampholytes under the influence of an electric potential. When performed in the capillary format, the use of smalldiameter capillaries with efficient dissipation of Joule heat permits the application of high field strengths for rapid focusing. The reduced convection in capillaries removes the requirement for gels. The use of UV-transparent fused silica capillaries enables direct on-tube optical detection of focused zones without the requirement for staining. The focusing effect provides resolving power up to 0.02 pI. A unique feature of cIEF with on-tube detection is the requirement for mobilization of the focused protein zones across the detector window.