CD-I strength does not contribute to the open state stability. (A and B) Normalized single-channel amplitude histogram of the corresponding traces (right) for WT (gray), R192A (blue), and R192A/H193D/T223R (red) at −50 mV (A) and average single-channel amplitudes (B). (C) Open interval distributions overlaid with the probability density function (thick line) from the entire corresponding recordings depicted in A. (D) The open state time constant (τ_o, ms, inset) and average MOT (ms) were calculated from fits to unbiased models consisting of three to four closed states and one open state (see Materials and methods). (B and D) Means ± SEM. (E) Microscopic recordings of R192A (left) and R192A/H193D/T223R (right) before and after onset of PIP₂ application (arrows).