The problem of accuracy in single-channel open probability measurements.

The function of ion channels to mediate the flux of ions through membranes of living cells depends on their number, conductance, and open probability. The open probability, P, characterizes gating of channels that is sensitive to experimental conditions and that can be determined in single-channel experiments. Individual experimental records and even whole series of single-channel activity measurements represent random samples of the stochastic gating continuous in time. The aim of this study was to understand the relationship between the accuracy (trueness and precision) of P determination and the method of single-channel activity data collection. We used simulated single-channel experiments with variable settings of data collection for a range of open probability values. We found that at low P, the trueness of P determination depends on the average number of channel openings per record, while the precision of P determination depends on the total number of channel openings in the whole dataset and on the distribution of open and closed times. We derived relationships that allow planning of single-channel experiments for the required accuracy of P determination over a large span of open probabilities.