(+)-18-Crown-6-tetracarboxylic acid (18C6TA) in the cytosolic solution eliminates long closed events in Kcv _NTS S42T. (A) Representative single-channel current traces from Kcv_NTS S42T at indicated membrane potentials in the absence (control) and presence of 200 µM 18C6TA in the cytosolic solution. Closed and open levels are marked by C and O, respectively. (B) Open probabilities of Kcv_NTS S42T in the absence (closed red circles) and presence (open red circles) of 200 µM 18C6TA in the cytosolic solution. Data points show arithmetic mean ± SD of three independent measurements. Individual data points are shown to the left of the mean values. (C) Representative closed dwell-time histograms from single-channel recordings of Kcv_NTS S42T at +160 mV before (control) and after addition of 200 µM 18C6TA. Both histograms are from the same experiment and were constructed from 5-min single channel traces. The number of detected events used to construct the dwell-time histograms are indicated. Histograms were fitted with three exponentials indicated with C1 (solid green line), C2 (solid blue line), and C3 (solid yellow line). Sums of all exponentials are shown as solid black lines. (D) Occupation probabilities of closed-time populations C2 (blue) and C3 (yellow) in the absence (closed circles) and presence (open circles) of 200 µM 18C6TA in the cytosolic solution. Data points show geometric mean ± geometric SD of three independent measurements. Individual data points are shown to the left of the mean values.