Fig. 5.
Diffusion constant of K+ relative to its value in the bulk as a function of the position along the channel axis. An analytical form fitted to the results from the simulations was used in the Brownian dynamics trajectories (dashed line). The absolute value of the calculated diffusion constant in bulk solution (0.37 Å2/ps) was uniformly scaled to the corresponding experimental value of 0.185 Å2/ps [Mills, R. & Lobo, V. (1989) Self-Diffusion in Electrolyte Solutions (Elsevier, Amsterdam)] in order to account for the underestimated viscosity of the TIP3P water model [Feller, S. E., Pastor, R. W., Rojnuckarin, A., Bogusz, S. & Brooks, B. R. (1996) J. Phys. Chem. 100, 17011–17020] at the temperature of the molecular dynamics simulations (330 K) [Bernèche, S. & Roux, B. (2001) Nature 414, 73–77].