Fig. 2.

Permeation of C₁₂TPP/palmitate ion pair through a POPC membrane (ABF molecular dynamics simulations). Shown are the lipid carbon tails (Thin Cyan Sticks), carbonyls and phosphates (Red and Brown Sticks), cholines (Blue Sticks), water molecules (Small Orange Spheres), C₁₂TPP (phenyl rings, Yellow; dodecyl residue, Green Spheres), palmitate (carboxyl oxygen, Magenta Spheres; hydrocarbon tail, Cyan Spheres). (A) Equilibrium structure obtained after 25 ns of unperturbed MD simulation was used as the starting configuration for the ABF analysis. (B) Structure after 30 ns of ABF simulation (conformation with largest distance between ions). (C) Final structure after 110 ns ABF simulation.