Figure 3. Ionic liquids induce bending of the lipid bilayer.

(a–c) Snapshots of coarse grained simulations of a POPC bilayer system (a) without ILs, (b) with [C₄mim]Cl and (c) with [C₁₀mim]Cl (top row). IL and NaCl (sodium-yellow; chloride-green) buffer concentrations are ~200 mM and ~160 mM respectively. In (c), a nearly fully covered monolayer of adsorbed [C₁₀mim]Cl is formed at the lipid bilayer aqueous interface. Coarse grained water molecules are not displayed. Interactions between IL cations with the POPC bilayer induce bending of the bilayer. The bilayer center of mass plane is shown in red to guide the eye. 3-D contour surface plots of the upper leaflet height based on the phosphate group of the lipid are plotted (bottom row). The lower leaflet surface is shown in gray. IL cations are only shown for clarity (imidazolium ring - blue; alkyl side chain - cyan). Z-coordinates have been recentered to the bilayer center plane. Spectral intensity based on the Fourier transform of the bilayer surface along the X and Y plane (bottom row inset). Intensity peaks corresponding to the bright red regions are associated with high amplitude bending modes of the bilayer surface.