The Effect of Methanol on Lipid Bilayers: An Atomistic Investigation

Abstract

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.

The influence of polyhydroxylated compounds on a hydrated phospholipid bilayer: a molecular dynamics study

“…27.8 and 5.6 m, respectively) and for POPC with ethanol ( [24]; molar ratio lipid:ethanol:water 1:1:10, i.e. 5.6 m) shows a decrease in the order parameters, in agreement with the trend observed for MET in the first simulation study [61]. The apparent contradiction between simulation and experimental results for ethanol ([62] vs. [24]) is rationalised by the authors [62] as being a consequence of the different concentration regimes and hydration levels considered.…”

“…This permits to investigate specifically the effect of the configurational (geometrical and stereochemical) restrictions imposed by a given molecular framework on the capacity of the CSL hydroxyl groups to interact with the lipid molecules. Note that, although, MD simulations of lipid bilayers in the presence of MET [60][61][62], GLU [57] and TRH [52][53][54][55][56][57][58] have been previously reported, the present work constitutes (to our knowledge) the first simulation study on the influence of ETG and GLY on membranes.…”

“…The apparent contradiction between simulation and experimental results for ethanol ([62] vs. [24]) is rationalised by the authors [62] as being a consequence of the different concentration regimes and hydration levels considered. The same argument may apply to the differences observed between the two simulation studies for MET ( [62] vs. [61]). A decrease in the order parameters, the magnitude of which increased with the alcohol concentration, was also observed in other simulation studies for MET (3 and 5 wt%, i.e.…”

“…With respect to the effect of MET on the order parameters of the lipid-tail carbon atoms, simulations have led to apparently contradictory results. The study of Pinisetty et al [61], performed at relatively high MET concentration (11.3 mol%, i.e. 6.3 m) for dipalmitoylphosphatidylcholine (DPPC) and palmitoyloleoylphosphatidylcholine (POPC) bilayers, reported a significant decrease in the order parameters compared to the pure hydrated systems (concomitant with a substantial increase of about 15% in the area per lipid).…”

Moving towards a Competitive Fully Enzymatic Biodiesel Process

“…In fact, for crude soybean oil, when methanol was present, the oil phase was completely clear and no sediment (gums) could be observed, contrarily to what happened to acid degummed or untreated samples, which displayed some turbidity or a sediment, respectively [80]. Therefore, methanol can solubilize the phospholipids of crude soybean oil [81], constituted mainly by PC (and to a lower extent by PE), described as easily hydratable phospholipids and also soluble in short-chain alcohols like ethanol [82]. The evidence of solubilization of phospholipids by methanol is of great importance in the process.…”