Under the Influence of Alcohol: The Effect of Ethanol and Methanol on Lipid Bilayers

Abstract

Extensive microscopic molecular dynamics simulations have been performed to study the effects of short-chain alcohols, methanol and ethanol, on two different fully hydrated lipid bilayer systems (POPC and DPPC) in the fluid phase at 323 K. It is found that ethanol has a stronger effect on the structural properties of the membranes. In particular, the bilayers become more fluid and permeable: ethanol molecules are able to penetrate through the membrane in typical timescales of approximately 200 ns, whereas for methanol that timescale is considerably longer, at least of the order of microseconds. A closer examination exposes a number of effects due to ethanol. Hydrogen-bonding analysis reveals that a large fraction of ethanols is involved in hydrogen bonds with lipids. This in turn is intimately coupled to the ordering of hydrocarbon chains: we find that binding to an ethanol decreases the order of the chains. We have also determined the dependence of lipid-chain ordering on ethanol concentration and found that to be nonmonotonous. Overall, we find good agreement with NMR and micropipette studies.

Molecular Dynamics Simulations of Ternary Membrane Mixture: Phosphatidylcholine, Phosphatidic Acid, and Cholesterol

“…See supplementary materials). The water density was depleted to near zero at z = ±10 Å, showing water penetration into the currently simulated bilayer at a similar depth as that observed in the previously simulated pure POPC system 51 . The electron density profile of POPC in the current system resembles the profile of pure POPC 51 , showing maximum electron densities of lipid head groups at z = ±15 Å.…”

“…The water density was depleted to near zero at z = ±10 Å, showing water penetration into the currently simulated bilayer at a similar depth as that observed in the previously simulated pure POPC system 51 . The electron density profile of POPC in the current system resembles the profile of pure POPC 51 , showing maximum electron densities of lipid head groups at z = ±15 Å. Therefore, the thickness of POPC in our ternary mixture and in the pure POPC system 51 is essentially the same, which makes the mechanism 52 that CHOL regulates protein-lipid hydrophobic matching by increasing the lipid bilayer thickness unlikely applicable to nAChR in the ternary mixture.…”

Drunken Membranes: Short-Chain Alcohols Alter Fusion of Liposomes to Planar Lipid Bilayers

“…Flip times for short-chain alcohols have not been directly measured; however, flip of ionized fatty acids has been reported to be no slower than seconds (69), and for unionized fatty acids on the millisecond timescale (70). Results from molecular modeling show flip of ethanol, propanol, and butanol on the submicrosecond timescale, depending on lipid composition (35,37,38). Additionally, butanol was observed to enhance fast phospholipid flip on the timescale of microseconds (38).…”

“…Molecular dynamics simulations (35)(36)(37)(38)(39) are one approach to look directly at the effects of alcohol on membranes. However as yet, these studies have only modeled the effects of alcohols on a single membrane and not their effect on the process of membrane fusion.…”

Evaluation of Chlorophyll Content, Antioxidant Activity and Phenolic Compounds in the Seedlings of Rice-type Tartary Buckwheat

“…The chlorophyll pigments are a major source applied in food and neutraceutical products (Mortensen, 2006). According to other findings the ethanol molecules penetrate lipidprotein bilayers more efficiently than methanol due to higher hydrophobicity (Patra et al, 2006). Therefore, we also used ethanol to extract the chlorophyll from the seedlings.…”