Biological signals that need detection: currents through single membrane channels

Single membrane channels are protein molecules that control movement in and out of cells. Picoamp currents flowing through just one of these channels are measured everyday in hundreds if not thousands of laboratories, thus allowing a remarkable resolution of important biological function. But currents through some of the most important channels are too small to measure with any ease. Currents through calcium channels are of the greatest importance in the function of the nervous system and in regulating the contraction of the heart and so are the target of many drugs used in clinical medicine. Yet calcium channel currents are just below the resolution of accurate measurement. Channel currents are detected in nearly all laboratories by a combination of low pass filtering and threshold detection. The medical and scientific payoff would be large indeed if more modem detection methods (e.g., wavelets) allowed the easy study of the small channels-e.g., the calcium channels-so important in disease and health