We have analyzed the signal transduction properties of voltage-dependent ion channels in the presence of an external electric noise source. Experiments were done with planar lipid bilayers modified by a well- studied channel-forming peptide, alamethicin. A current response to a small sine-wave voltage signal was measured at different levels of admixed """"""""white"""""""" noise. We showed that addition of external noise to this system input induces a significant increase of signal component at its output. This noise-induced enhancement in signal transduction does not decrease the output signal-to-noise ration and shows some features of the 'stochastic resonance'. As we showed previously using phospholipid species with different tendency to form non-lamellar structures, alamethicin channels are sensitive to the inherent stress of Lipid packing within a membrane. Now, studying conductance probability distribution of alamethicin channels incorporated into a charged lipid membrane and varying charge per lipid molecule via pH of the membrane-bathing solution, we are able to relate quantatively the channel conformational equilibrium seen in its opening and closing statistics to the membrane pacing energetics. An immediate consequence of these studies is the ability to observe how a single macromolecular unit is able to time.average the binding and dissociation of small molecular weight effectors.
