Figure 8.

Lateral MSD of the excess proton at various membrane penetration depths shows that the diffusion rate increases as the proton leaves the membrane. The MSD at 2.5 nm is the average lateral MSD in bulk water and we could only obtain the MSD at 2.25 nm over 50 ps due to sampling problems. To illustrate the excess protons penetration depth the density profiles normal to the membrane surface of the hydronium, water, lipid tails, and lipid headgroups are plotted in the background (also shown in Fig. 1). To see this figure in color, go online.