PHYSICS OF IONIC CHANNELS AND OTHER PROTEINS WITH AQUEOUS CAVITIES

点击翻译按钮获取中文摘要

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 alamethicin a well studied channel-forming peptide. 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 transductiion does not decrease the output signal-to-noise ratio and shows some features of the stochastic resonance. As we have previously shown by using phospholipid species with different tendency to form non-lamellar structures, alamethicin channels are sensitive to the inherent stress of lipid packing with a membrane. We are able to relate quantitatively the channel conformational equilibrium seen in its opening and closing statistics to the membrane packing energetics. This is done through the study of statistical characteristics of alamethicin channels incorporated into a charged lipid membrane. In these experiments the charge per lipid molecule is changed by varying the pH of the membrane-bathing solution.