PHYSICS OF IONIC CHANNELS AND OTHER PROTEINS WITH AQUEOUS CAVITIES

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Membrane channel proteins appear to "open" and "close" by collapsing the aqueous cavity through which ions flow. That picture, derived from earlier studies on mitochondrial and axon proteins, has now been seen via osmotic stress studies on the alpha-toxin protein. Widening the purview of our investigation on proteins whose control derives from different accessibility of the surface to water solvent, we have measured a shift in the uptake of oxygen by hemoglobin when the molecule is subject to lowered activity of water. In this way we have measured an increase of 60 to 80 water molecules associated with hemoglobin when it loads oxygen. During the past year, too, we have developed apparatus to detect membrane electrical "noise" as a source of information on the activity of large populations of channels.