Figure 6.
Electrostatic potential at ±200 mV membrane potential. (a) 2D-electrostatic potential maps (vector 1,0,1 in Cartesian space). (b) The 3D-electrostatic potential at +200 mV overlaid onto the solvent mass density isosurface. The color scale is −12.11 to 32.95 kT/e (−323 to +880 mV) from blue to red. Only the electrostatic potential at +200 mV is shown here as the color change in −200 mV is much less prominent (because of the opposite orientation of the intrinsic dipole as described in the text). (c) Electrostatic potential overlaid onto the cAMP density isosurface at +200 mV. The color scale is −267 to +267 mV. The isosurface contour cutoff is 0.1 amu/Å3 for (b and c). All data in this figure are calculated from the 3D electrostatic potential map (r) based on all charged atoms in the simulated system by solving Poisson equation on a 1-Å resolution grid using the VMD PMEPot plugin (76). PMEPot approximate point charge by a spherical Gaussian with an Ewald factor of 0.25. (r) is reported as the average of 1000 snapshots from the last 200 ns. To see this figure in color, go online.