The effect of methanol on lipid bilayers: an atomistic investigation.

The interactions of methanol with lipid bilayers were studied by means of molecular dynamics (MD) simulations. Our MD simulations focus on the effect of approximately 11.3 mol% methanol on two fully hydrated dipalmitoylphosphatidylcholine (DPPC) and palmitoyloleoylphosphatidylcholine (POPC) lipid bilayers both in the fluid phase and under equilibrium conditions at 323 and 298 K, respectively. The effects of methanol on bilayers structural characteristics were investigated. In both systems the simulations show that the presence of relatively high concentration of methanol leads to a significant increase in the area per lipid. The increase in the area per lipid is accompanied by a corresponding decrease of the bilayer thickness such that the volume occupied per lipid does not change significantly in the presence of methanol. Other properties such as ordering of phospholipid tails and lateral diffusion of the lipids are also affected significantly by the presence of methanol. Consistent with other previously reported MD simulation studies of bilayers in the presence of methanol (albeit at a significantly smaller concentration of 1 mol%) our study shows very few hydrogen bonding formation between lipids and methanol.