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Soft Matter and Biological Physics
Eur. Phys. J. E 3, 37-44 (2000)
DOI: 10.1007/s101890070039

A molecular model for the line tension of lipid membranes

S. May

Institut für Biochemie und Biophysik, Friedrich-Schiller-Universität Jena, Philosophenweg 12, Jena 07743, Germany


(Received 2 January 2000)

Abstract
The line tension of a symmetric, lipid bilayer in its liquid-crystalline state is calculated on the basis of a molecular lipid model. The lipid model extends the opposing forces model by an expression for the conformational free energy of the hydrocarbon chains. We consider a membrane edge that consists of a perturbed bilayer covered by a section of a cylinder-like micelle. The structural rearrangement of the lipids implies an excess free energy which we minimize with respect to the cross-sectional shape of the membrane edge, including both the micellar and the bilayer region. The line tension is derived as a function of molecular lipid properties, like the lipid chain length or the head group interaction strength. We also relate it to the spontaneous curvature of the lipid layer. We find the line tension to become smaller for lipid layers that tend to curve more towards the hydrophobic core. Our predictions for the line tension and their relation to experimentally derived values are discussed.

PACS
87.16.-b - Subcellular structure and processes.
68.10.-m - Fluid surfaces and fluid-fluid interfaces.
68.10.Et - Interface elasticity, viscosity, and viscoelasticity.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2000