A Combined Molecular Dynamics and Diffusion Model of Single Proton Conduction through Gramicidin

AbstractWe develop a model for proton conduction through gramicidin based on the molecular dynamics simulations of Pomès and Roux (Biophys. J. 72:A246, 1997). The transport of a single proton through the gramicidin pore is described by a potential of mean force and diffusion coefficient obtained from the molecular dynamics. In addition, the model incorporates the dynamics of a defect in the hydrogen bonding structure of pore waters without an excess proton. Proton entrance and exit were not simulated by the molecular dynamics. The single proton conduction model includes a simple representation of these processes that involves three free parameters. A reasonable value can be chosen for one of these, and the other two can be optimized to yield a good fit to the proton conductance data of Eisenman et al. (1980, Ann. N.Y. Acad. Sci. 339:8–20) for pH≥1.7. A sensitivity analysis shows the significance of this fit