Effect of Na+ and Ca2+ Ions on a Lipid Langmuir Monolayer: An Atomistic Description by Molecular Dynamics Simulations |
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Authors: | Juan José Giner Casares Luis Camacho Prof. Dr. Maria Teresa Martín‐Romero Prof. Dr. José Javier López Cascales Prof. Dr. |
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Affiliation: | 1. Universidad de Córdoba, Departamento de Química Física y Termodinámica Aplicada, Ed. Marie Curie, Campus de Rabanales, 14014. Córdoba (Spain);2. Universidad Politécnica de Cartagena, Bioinformatic and Macromolecules Group (BIOMAC), Area de Química Física, Aulario II, Campus de Alfonso XIII, 30203 Cartagena, Murcia (Spain), Fax: (+34)?968?325?931 |
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Abstract: | Studying the effect of alkali and alkaline‐earth metal cations on Langmuir monolayers is relevant from biophysical and nanotechnological points of view. In this work, the effect of Na+ and Ca2+ on a model of an anionic Langmuir lipid monolayer of dimyristoylphosphatidate (DMPA?) is studied by molecular dynamics simulations. The influence of the type of cation on lipid structure, lipid–lipid interactions, and lipid ordering is analyzed in terms of electrostatic interactions. It is found that for a lipid monolayer in its solid phase, the effect of the cations on the properties of the lipid monolayer can be neglected. The influence of the cations is enhanced for the lipid monolayer in its gas phase, where sodium ions show a high degree of dehydration compared with calcium ions. This loss of hydration shell is partly compensated by the formation of lipid–ion–lipid bridges. This difference is ascribed to the higher charge‐to‐radius ratio q/r for Ca2+, which makes ion dehydration less favorable compared to Na+. Owing to the different dehydration behavior of sodium and calcium ions, diminished lipid–lipid coordination, lipid–ion coordination, and lipid ordering are observed for Ca2+ compared to Na+. Furthermore, for both gas and solid phases of the lipid Langmuir monolayers, lipid conformation and ion dehydration across the lipid/water interface are studied. |
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Keywords: | cations interfaces lipids molecular dynamics monolayers |
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