Figure 13.

Computer simulation of the time-dependent block by β4_154–167 at 50 mV. (A) Normalized open probability against time is shown. Normalized probabilities for transient closed and open blocked states are also included. Data were generated by the MATLAB software according to Scheme 1 with α = 1.6 e^V/40, β = 0.3 e^−V/40, γ = 50 e^V/100, and δ = 0.6 e^−V/25, where V is in millivolts. The β4_154–167 concentration is set at 125 μM; rate constants are the same as described in Fig. 2 A. (B) The time-dependent block during the pulse can be fitted by a single exponential function, τ = 0.86 ms. (C) The plot of 1/τ against β4_154–167 concentration shows a nonlinear relationship. The difference on the saturation level between Fig. 2 B and Fig.13 C is likely inherent because rate constants for binding were extracted by linear regression and because the voltage coefficients were obtained by repetitive approximation.