The Effects of NaCl on Oxidized Lipid Bilayers

Abstract

Lipid peroxidation plays an important role in cell membrane damage in which the polyunsaturated lipids are the main target for free radicals. The lipid bilayer systems of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC) and its 4 main oxidation products, namely 9-tc-hydroperoxide linoleic acid, 13-tc-hydroperoxide linoleic acid, 9-oxononanoic acid, and 12-oxo-9-didecadienoic acid were used to study the properties of oxidized lipid bilayer {Wong-ekkabut J., et al., Biophys. J., 2007 }. Our study showed that the oxidized lipid molecules were able to change the physical and mechanical properties of lipid bilayer. The effect of salt ions, important in living cells, have not been studied previously. Here, the effects of NaCl on the properties of oxidized lipid bilayers were studied by using molecular dynamics simulations. We found that the effects of the oxidized lipids in the bilayer were in good agreement with the previous studies {Wong-ekkabut J., et al., Biophys. J., 2007 }. The increasing concentrations of the oxidized lipids caused an increase of the area per lipid and a decrease of the bilayer thickness. A stable water defect was formed in the bilayer at a high concentration of oxidized lipids because the polar group in the oxidized lipid tail attracted the water dipoles. When salt molecules were added, sodium ions permeated into the head group region leading to a decrease of the area per lipid and an increase of the bilayer thickness. Our results show that salt ions decrease membrane fluidity and water permeability of the oxidized lipid bilayer.