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Int. J. Mol. Sci. 2013, 14(2), 2846-2861; doi:10.3390/ijms14022846
Article

Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations

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Received: 22 December 2012; in revised form: 20 January 2013 / Accepted: 21 January 2013 / Published: 29 January 2013
(This article belongs to the Special Issue Self-Assembled Soft Matter Nanostructures at Interfaces)
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Abstract: The lipid bilayer is a basic building block of biological membranes and can be pictured as a barrier separating two compartments filled with electrolyte solution. Artificial planar lipid bilayers are therefore commonly used as model systems to study the physical and electrical properties of the cell membranes in contact with electrolyte solution. Among them the glycerol-based polar phospholipids which have dipolar, but electrically neutral head groups, are most frequently used in formation of artificial lipid bilayers. In this work the electrical properties of the lipid layer composed of zwitterionic lipids with non-zero dipole moments are studied theoretically. In the model, the zwitterionic lipid bilayer is assumed to be in contact with aqueous solution of monovalent salt ions. The orientational ordering of water, resulting in spatial variation of permittivity, is explicitly taken into account. It is shown that due to saturation effect in orientational ordering of water dipoles the relative permittivity in the zwitterionic headgroup region is decreased, while the corresponding electric potential becomes strongly negative. Some of the predictions of the presented mean-field theoretical consideration are critically evaluated using the results of molecular dynamics (MD) simulation.
Keywords: lipids; dipolar zwitterionic headgroups; relative permittivity; orientational ordering; water molecules; planar lipid bilayers lipids; dipolar zwitterionic headgroups; relative permittivity; orientational ordering; water molecules; planar lipid bilayers
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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MDPI and ACS Style

Velikonja, A.; Perutkova, Š.; Gongadze, E.; Kramar, P.; Polak, A.; Maček-Lebar, A.; Iglič, A. Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations. Int. J. Mol. Sci. 2013, 14, 2846-2861.

AMA Style

Velikonja A, Perutkova Š, Gongadze E, Kramar P, Polak A, Maček-Lebar A, Iglič A. Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations. International Journal of Molecular Sciences. 2013; 14(2):2846-2861.

Chicago/Turabian Style

Velikonja, Aljaž; Perutkova, Šarka; Gongadze, Ekaterina; Kramar, Peter; Polak, Andraž; Maček-Lebar, Alenka; Iglič, Aleš. 2013. "Monovalent Ions and Water Dipoles in Contact with Dipolar Zwitterionic Lipid Headgroups-Theory and MD Simulations." Int. J. Mol. Sci. 14, no. 2: 2846-2861.


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