Representative closed dwell-time distributions at different cytoplasmic pH and [Ca²⁺]. Smooth curves represent fits of these data with mixtures of one to four exponential components (with indicated time constants [τ] and fractional areas). Distributions from bilayers containing more than one active channel (n > 1) were generated from data that showed only a single open current level; thus, for n > 1, the true durations of long closings are “N” times the observed durations. These data illustrate that closed times are typically comprised of one or more long lifetime components and one or more brief lifetime components (“flickers”); the durations of flickers appear independent of [Ca²⁺] and pH ([H⁺]), whereas the durations and frequency of longer closings decrease with higher [Ca²⁺] and higher pH (i.e., lower [H⁺]). The number of fitted intervals in the distribution were: pH 6.5, 5 mM, 83 events; pH 6.5, 10 mM, 4,024 events; pH 6.5, 30 mM, 5,696 events; pH 7.3, 2 mM, 230 events; pH 7.3, 3 mM, 2,453 events; pH 7.3, 30 mM, 5,528 events; pH 8.1, 0.7 mM, 1,202 events; pH 8.1, 1 mM, 2,569 events; pH 8.1, 10 mM, 7,386 events.