Under the influence of alcohol: The effect of ethanol and methanol on lipid bilayers

¹ Helsinki University of Technology
² Helsinki University of Technology and Helsinki Institute of Physics
³ University of California at Davis
⁴ University of Helsinki

^* To whom correspondence should be addressed. E-mail: mikko.karttunen{at}hut.fi.

Submitted on March 4, 2005
Revised on March 29, 2005
Accepted on 26 July 2005

	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 323K. 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 time scales of about 200 ns whereas for methanol that time scale 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 are 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 non-monotonous. Overall, we find good agreement with NMR and micropipette studies.

Key Words: anesthesia, dppc, ethanol, methanol, molecular dynamics, popc

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