Scheme I describes the single-channel data under different experimental conditions. (A) Distinguishing between gating mechanisms with dependency difference plots. (top) Dependency difference plots for schemes I, II, and IR obtained by simulating and analyzing one million intervals (left three) and for representative experimental data at 40 mV and 20°C (right). (middle) Dependency difference plots obtained by rotating the top plot toward the closed times and projecting the image on a vertical plane parallel to the closed-time axis. (bottom) Schemes to be compared. In scheme IR, the position of the long opens and brief opens has been interchanged with respect to scheme I. The LL values are indicated below the plots for that scheme. Scheme I, with the best LL, gives the best approximation of the experimental data. OB and OL indicate briefer and longer open states, respectively. Compare with Fig. 5 for axis labeling. Note that log open times increase from right to left, and log closed times increase from left to right. (B) Schematic representation of the change in the rate constants of scheme I with increasing voltage and at a fixed temperature of 20°C. The areas of the states are proportional to the equilibrium occupancies estimated from the models. The thicker (red) arrows indicate a significant increase in the rate constant. The smaller (green) arrow indicates a significant decrease. The orange arrow indicates the dominant change observed with increasing voltage. The values for these changes are shown in Table IV. The mean parameters in Table IV were calculated from parameters obtained from eight separately analyzed channels.