Fluctuation-dissipation theorem imposes high-voltage fluctuations in biological ionic channels

Abstract

In order to determine the voltage fluctuations across cell membranes, the theory of generalized susceptibility was applied to a system consisting of a capacitor and a resistor in parallel, resembling a fragment of biological cell membrane harboring an ionic channel. We found, in accordance with others, that the mean square voltage fluctuation is given by 〈${\mathit{V}}^2$〉=kT/C, where C is the electrical capacitance of the membrane. When the above equation is applied to different combinations of membrane patch areas and corresponding channels, it is possible to identify a range of membrane areas and channel conductivities where voltage fluctuations may influence the behavior of a putative gate. It appears that for lower channel conductivities high amplitude voltage fluctuations fall in the range of typical gating response times. It is proposed that voltage fluctuations may be included among the many mechanisms influencing gating behavior.