Concentration dependence for Zn²⁺ effects on activation voltage sensitivity. (A) Concentration dependence for the increase in activation slope factor (k_act) determined under the experimental conditions indicated on the right (same cells as in Fig. 8). Solid lines are binding isotherms for a simple bimolecular reaction. (B and C) Extrapolated maximum increase (E_max; B) and logarithm of apparent dissociation constants (logK_Zn; C) obtained from fits to the data in A. Shown are best-fit values and 84% CIs.