FIGURE 11.

A model of the wild-type channel with the addition of a second region of positive charge. (A) The voltage profile of the pore of a channel calculated with the PNP model of Chen and Eisenberg (1993) using 199 points at holding potentials of 0, ±50, ±100, ±150 mV with a positive charge centered at a distance of 0.4 and a second region of positive charge centered at 0.15 (see text for details). This corresponds to a simple model of either the T8R or T8K channel. (B) The first derivative (dV/dD) of each of the voltage profiles shown in A are plotted as a function of distance. The uppermost trace is the derivative of the −150-mV voltage profile. The derivative was determined by a numerical procedure contained in Microcal Origin 6.0 software using a second order polynomial smoothing function utilizing 10 points. Plots of derivatives are in descending order from −150 to 150 mV. (C) Bar graph of the values of the derivatives for each curve in B at distances of 0.15 and 0.4. (D) Bar graph of the net force acting on both charged regions, obtained by the summation of forces shown in panel C. (E) The voltage profile of the pore of a channel calculated with the PNP model of Chen and Eisenberg (1993) using 199 points at holding potentials of 0, ±50, ±100, ±150 mV with a positive charge centered at a distance of 0.4 and a second region of positive charge centered at 0.2 (see text for details). This would approximate the G5R channel. (F) Bar graph of the net force acting on both charged regions.