Five-state gating polarity model does not fit conditions where VSD is constant. (A) Gating scheme of the five-state gating polarity model. Voltage-dependent steps, K1 and K2, are bolded to indicate constrained values (i.e., K1 and K2 parameter values used for fitting HHHEH are applied to all HHHE-X chimeras). K3 and K4 are voltage-independent transition steps and vary in each chimera. Abbreviations for each state and equations for calculations of open probabilities are the same as Fig. 4 A. Fitting of PO−V scatter plot data to the gating scheme described in A is shown in the following panels as a solid black line. Parameter values used in these fittings are in Table S2. PO−V scatter plot data are adapted from Lin et al. (2024). (B–G)PO−V scatter plot of HHHEH (diamond ♦), HHHEH2 (downward-pointing triangle ▼), HHHES (asterisk *), HHHER (right-pointing triangle ►), HHHEK (pentagram ★), and HHHEA (left-pointing triangle ◄). (i–iii) Collection of PO−V plots in F and G, such that K3 = 1 × 10−7 and K4 is varied to the following parameter values: (i) K4 = 1, (ii) K4 = 10, and (iii) K4 = 100.