Frequencies of paired open-closed durations of ion channels. Method of evaluation from single-channel recordings.

The probability of the occurrence of consecutive closed-open or open-closed intervals of specified durations in single-channel recordings may be of enormous help in the establishment of the kinetic scheme that describes the behavior of the channel. The relevant probability functions are linear combinations of products of exponential functions of the closed durations and the open durations. A method is presented for the evaluation of the coefficients of the exponential functions using a set of auxiliary functions that are each orthogonal to all but one of the exponential functions. The coefficients in the probability functions may then be obtained from the experimental data by multiplication by the auxiliary functions and subsequent simple integration operations. Furthermore, the variance to be expected in the evaluated numerical magnitude of the parameters, due to the stochastic nature of the transitions in the channel conductance, is also readily estimated by use of the above auxiliary functions. The procedure is illustrated by analysis of synthetic data obtained from computer simulated experiments.