A layer model of ethanol partitioning into lipid membranes

Abstract

Abstract. The effect of membrane composition on ethanol partitioning into lipid bilayers was assessed by headspace gas chromatography. A series of model membranes with different compositions have been investigated. Membranes were exposed to a physiological ethanol concentration of 20 mmol/l. The concentration of membranes was 20 wt% which roughly corresponds to values found in tissue. Partitioning depended on the chemical nature of polar groups at the lipid/water interface. Compared to phosphatidylcholine, lipids with headgroups containing phosphatidylglycerol, phosphatidylserine, and sphingomyelin showed enhanced partitioning while headgroups containing phosphatidylethanolamine resulted in a lower partition coefficient. The molar partition coefficient was independent of a membrane's hydrophobic volume. This observation is in agreement with our previously published NMR results which showed that ethanol resides almost exclusively within the membrane/water interface. At an ethanol concentration of 20 mmol/l in water, ethanol concentrations at the lipid/water interface are in the range from 30-15 mmol/l, corresponding to one ethanol molecule per 100-200 lipids.

DnaK and GroEL chaperones are recruited to the Bacillus subtilis membrane after short-term ethanol stress

“…The markedly increased membrane rigidity after application of 3% ethanol can also be explained in terms of direct interaction of alcohol molecules with the membrane. Ethanol is preferentially embedded within the membrane–water interface, but the bilayer interior can also be disordered (Klemm and Williams 1996; Nizza and Gawrisch 2009). In our case, the anisotropy of DPH showed the markedly decreased fluidity of the membrane interior that probably induced the concurrent perturbation of proper functions of membrane proteins as documented by the recruitment of protein chaperones on the cytoplasmic membrane.…”

Partitioning of ethanol into lipid membranes and its effect on fluidity and permeability as seen by X-ray and neutron scattering

“…Our knowledge about interactions between ethanol and lipid membranes on the molecular scale mainly stems from two techniques: nuclear magnetic resonance (NMR) experiments [1][2][3] and molecular dynamics (MD) simulations. [4][5][6][7][8][9] In particular, experiments using neutron and X-ray scattering to probe molecular dynamics and structure are scarce, [10][11][12] most likely due to experimental challenges.…”

The Interaction of Bio-Molecules with Lipid Membranes Studied by X-ray Diffraction

“…For this reason, highly concentrated suspensions of 1,2-dimyristoyl-sn-glycero-3-phoshatidylcholine (DMPC) were prepared by hydrating the lipid powder using a 5 wt % ethanol solution, as shown in Figure 1a. This concentration is significantly larger than alcohol concentrations of ∼0.092 wt % (∼0.036 mol %) found in human blood [30]. However, 5 wt % can be considered a moderate alcohol concentration to which skin and mucous membranes in mouth and digestive system can be exposed.…”

“…Two-dimensional data sets were collected to study molecular structure perpendicular to the solid supported membranes (out-of-plane, ) and parallel to the membranes (in-plane, || ). c) Reflectivity measurement for samples containing 3 mol % A [25][26][27][28][29][30][31][32][33][34][35] . Fourier transforms of the reflectivity data using the shown phases (inset) provides the electron density perpendicular to the membrane.…”

“…In the fluid phase at = 303 K (Figure 1 Measuring membrane/ethanol and membrane/water partition coefficients in the presence of ethanol has proven to be difficult due to experimental challenges, mainly related to the small volumes and the volatility of the ethanol molecule. Partition coefficients must be measured in-situ, directly on lipid bilayers [30,[40][41][42][43][44][45]. X-ray diffraction can quantitatively determine partition coefficients of small molecules in membranes in their physiologically relevant fluid phase.…”