Figure 8.

The G466A/V467G mutations have little effect on the voltage dependence of TPentA block. Steady-state block at voltages between +20 and +80 mV from inside-out patch currents as in Fig. 7. The data were fit by the equation F _un/(1 − F _un) = C · exp(−δVF/RT), where F _un is the steady-state fraction of unblocked current, C is a constant, and δ is a unitless parameter representing the fraction of the electric field at the blocking site felt by the blocker and any ions that move with it. The estimates of δ were 0.15 ± 0.01 and 0.18 ± 0.03 for WT and G466A/V467G, respectively, for n = 3 patches each. These values are not significantly different (P > 0.05, t test).