Figure 5.

The relationship between catch-and-hold and preopen states. (A) Scheme 4 was used to simulate single-channel currents. AR^H, AF², and AF³ each had a lifetime of 0.8 µs, and AR^L and AR* (the only open-channel state) had a lifetime of 2 ms. In this model, the forward hold conformational change (AR^L→AR^H) is the first step of a flip sojourn in the entire transition-state ensemble. (B; left) An example burst of openings shown at different sampling frequencies. The idealized current trace (determined after filtering to half of the sampling frequency) is shown below; n is the number of detected shut intervals in each burst. (Right) Shut-interval duration histograms from the idealization. At all sampling frequencies, a long-lived shut component is apparent that corresponds to sojourns in AR^L. The briefer components reflect sojourns in the aggregate [AR^H, AF², AF³] that merge into a single flip event with decreasing sampling rates. At 200 kHz, there is only a single ∼4-µs gap apparent.