Biological-to-electronic interface with pores of ATP synthase subunit C insilicon nitride barrier

An oscillator pore is identified that generates intermittent, large amplitu de, ionic current in the plasma membrane. The pore is thought to be compose d of 10-12 units of subunit c of ATP synthase. Pore opening and closing is a co-operative process, dependent on the release, or binding, of as many as six calcium ions. This mechanism suggests a more general method of co-oper ative threshold detection of chemical agents via protein modification, the output being directly amplified in a circuit Here the authors describe step s in the development of a sensor of chemical agents. The subunit c pore in a lipid bilayer spans a nanometer-scale hole in a silicon nitride barrier. Either side of the barrier are electrolyte solutions and current through th e pore is amplified by circuitry. The techniques of laser ablation, electro n beam lithography and ion beam milling are used to make successively small er holes to carry the lipid patch. Holes of diameter as small as 20 nm are engineered in a silicon nitride barrier and protein activity in lipid membr anes spanning holes as small as 30nm in diameter is measured. The signal-to -noise ratio of the ionic current is improved by various measures that redu ce the effective capacitance of the barrier. Some limits to scale reduction are discussed.