Application of dwell-time series in studies of long-range correlation in single channel ion transport: analysis of ion current through a big conductance locust potassium channel

The time series of successive closed- and open-states durations determined for a voltage-dependent big conductance locust potassium channel (BK channe l) have been analyzed. The problem of correlation between the states have b een discussed by means of the autocorrelation function, Hurst and detrended fluctuation analysis (DFA) as well as surrogate data tools. We showed that the existence of correlation between closed and open times can be detected only by simultaneous application of several different tools. All technique s pointed at a stronger correlation, therefore longer memory, in the series of closed states. Persistent character of both examined dwell-time series has been shown by the Hurst and DFA analyses, whose exponents were found si gnificantly larger than 0.5 - a value typical for random walk. It may origi nate from the externally applied electric field, which directs ion movement and influences channel kinetics. DFA detected two ranges of different corr elations in the series of closed states durations. This result points to th e existence of two processes with different correlation characteristics whi ch govern the channel functioning. The DFA exponent equal to 0.86 +/- 0.07 for long-range scaling of closed times suggests that the long memory of the BK channel action arising from the dichotomous nature of the signal and th e long-tail properties of the closed-times distribution can be also governe d by the correlation between closed states. The possible biological implica tions of the findings have been also discussed. (C) 2001 Elsevier Science B .V. All rights reserved.