O. Orwar, K. Jardemark, C. Farre, I. Jacobson, A. Moscho, J. B. Shear, H. A. Fishman, S. J. Lillard, and R. N. Zare,”Voltage Clamp Biosensors for Capillary Electrophoresis,” Methods in Enzymology 294,189-208 (1998).