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Issue 30, 2012
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Modeling the influence of adsorbed DNA on the lateral pressure and tilt transition of a zwitterionic lipid monolayer

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Abstract

Certain lipid monolayers at the air–water interface undergo a second-order transition from a tilted to an untilted liquid-crystalline state of their lipid hydrocarbon chains at sufficiently large lateral pressure. Recent experimental observations demonstrate that in the presence of divalent cations DNA adsorbs onto a zwitterionic lipid monolayer and decreases the tilt transition pressure. Lowering of the tilt transition pressure indicates that the DNA condenses the lipid monolayer laterally. To rationalize this finding we analyze a theoretical model that combines a phenomenological Landau approach with an extension of the Poisson–Boltzmann model to zwitterionic lipids. Based on numerical calculations of the mean-field electrostatic free energy of a zwitterionic lipid monolayer–DNA complex in the presence of divalent cations, we analyze the thermodynamic equilibrium of DNA adsorption. We find that adsorbed DNA induces a 10% reduction of the electrostatic contribution to the lateral pressure exerted by the monolayer. This result implies a small but notable decrease in the tilt transition pressure. Additional mechanisms due to ion–ion correlations and headgroup reorientations are likely to further enhance this decrease.

Graphical abstract: Modeling the influence of adsorbed DNA on the lateral pressure and tilt transition of a zwitterionic lipid monolayer

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Publication details

The article was received on 23 Mar 2012, accepted on 30 May 2012 and first published on 30 May 2012


Article type: Paper
DOI: 10.1039/C2CP40923B
Phys. Chem. Chem. Phys., 2012,14, 10613-10621

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    Modeling the influence of adsorbed DNA on the lateral pressure and tilt transition of a zwitterionic lipid monolayer

    K. Bohinc, G. Brezesinski and S. May, Phys. Chem. Chem. Phys., 2012, 14, 10613
    DOI: 10.1039/C2CP40923B

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