Issue 42, 2012

Effect of heavy water on phospholipid membranes: experimental confirmation of molecular dynamics simulations

Abstract

Although there were experimental indications that phospholipid bilayers hydrated with D2O express different biophysical properties compared with hydration by ordinary H2O, a molecular concept for this behavior difference was only recently proposed by a molecular dynamics simulations study [T. Róg et al., J. Phys. Chem. B, 2009, 113, 2378–2387]. Here we attempt to verify those theoretical predictions by fluorescence measurements on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes. Specifically, we determine the water isotope effect on headgroup hydration and mobility, lateral lipid diffusion and lipid backbone packing. Time-dependent fluorescence shift experiments show significantly slower dynamics and lower hydration of the headgroup region for a bilayer hydrated with D2O, an observation in good agreement with the calculated predicted differences in duration of lipid–lipid and lipid–water bridges and extent of water penetration into the bilayer, respectively. The water isotope effect on the lipid order parameter of the bilayer core (measured by fluorescence anisotropy) and lateral diffusion of lipid molecules (determined by two-focus fluorescence correlation spectroscopy) is close to the experimental errors of the experiments, however also refers to slightly more rigid organization of phospholipid bilayers in heavy water. This study confirms the view that the water isotope effect can be particularly found in time-resolved physicochemical properties of the membrane. Together with the simulations our experiments provide a comprehensive, molecular view on the effect of D2O on phospholipid bilayers.

Graphical abstract: Effect of heavy water on phospholipid membranes: experimental confirmation of molecular dynamics simulations

Article information

Article type
Paper
Submitted
20 4 2012
Accepted
19 7 2012
First published
19 7 2012

Phys. Chem. Chem. Phys., 2012,14, 14516-14522

Effect of heavy water on phospholipid membranes: experimental confirmation of molecular dynamics simulations

L. Beranová, J. Humpolíčková, J. Sýkora, A. Benda, L. Cwiklik, P. Jurkiewicz, G. Gröbner and M. Hof, Phys. Chem. Chem. Phys., 2012, 14, 14516 DOI: 10.1039/C2CP41275F

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