Background gating properties of WT and Y1795C mutant channels. (a) Experimentally observed WT (left) and Y1795C (right) single channels in the background mode. (b) MOTs of experimentally measured (top) and simulated (bottom) channels in the background mode (i.e., non-burst mode) at –30 mV. Histograms (bin size = 200 microseconds) were generated from all events (500–1,000 sweeps) for each construct. Only patches containing fewer than three channels were used to generate histograms. MOT was determined by single exponential fits to the experimental data. The time constants extracted from the fits were: Y1795C, 0.97 ± 0.05 milliseconds, n = 6; WT, 0.50 ± 0.05 milliseconds, n = 7. The computation (lower panel) accurately simulates mutation-induced prolongation of MOT (Y1795C, 1.01 milliseconds; WT, 0.50 milliseconds). The MOT is determined theoretically by the single exponential function e^–t/τ where τ = 1/sum of transition rates out of the open state. τ, time constant.