Determination of single-pore conductance from noise analysis. Influence of distribution in pore-amplitudes

For pores which can adopt only the open and closed states, the influence of the amplitude distribution of the single-pore conductance (gamma, open state) on the covariance function is derived. It is shown that reliable mean values of gamma (E(gamma)) can be derived from noise analysis only if the variance in the amplitude distribution (sigma gamma (2)) is known. In the past, sigma gamma (2) was set always to zero, leading to an overestimation of E(gamma). In the case of gramicidin-doped lipid bilayer membranes, this overestimation amounts to as much as 15% of the true value of E(gamma).