Electrochemical release from gold-thiolate electrodes for controlled insertion of ion channels into bilayer membranes

A proof-of-principle experiment to inject a sub-attomole amount of a channel compound into a bilayer membrane is described. The system is based on reductive cleavage of a self-assembled gold-thiol monolayer. In 'macroscopic' experiments, 11-biphenyloxyundecane thiol formed well-ordered monolayers by open-circuit or controlled potential deposition. The products of reductive release were determined by chromatographic analysis. In DMF, the sole reduction product is the corresponding disulfide. In acetonitrile and water, only the thiol is detected. The current efficiency is low due to competing electrolysis of water, and to the low solubility of the released thiol or disulfide layer. On a 'microscopic' scale, the half ester of dithiodibutyric acid with gramicidin was deposited on a gold microelectrode under open circuit conditions. The thoroughly washed microelectrode, placed in proximity to a bilayer, released gramicidin only following a 100 ms pulse of reducing potential. The transfer efficiency of this method for controlled positioning of ion channels is estimated to be better than 1 part in 10(5).