Fits with a flip model containing two binding sites (Scheme 2). (A) Scheme 2 is a flip model with two binding sites and a single open state that can be accessed from the fully liganded shut state after flipping. (B) Plots that show open-period and shut-time distributions fitted with Scheme 2. The same set of four patches is used as in Fig. 3 B for comparison. The fits with Scheme 2 are performed using constraints for non-interacting binding sites (resolution, 20 µs). (C and D) Simulation of a single-channel record (at 20 µM glycine) using the fitted rate constants of two of the sets fitted with Scheme 2 (the set in D is the one shown in the histograms). The predictions from all sets fitted with this model are in a very good agreement with the observed single-channel records (compare with Fig. 2 A).