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arXiv · 0706.3090

Flexible-to-semiflexible chain crossover on the pressure-area isotherm of lipid bilayer

I. N. Krivonos·S. I. Mukhin
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Abstract

We found theoretically that competition between ~Kq^4 and ~Qq^2 terms in the Fourier transformed conformational energy of a single lipid chain, in combination with inter-chain entropic repulsion in the hydrophobic part of the lipid (bi)layer, may cause a crossover on the bilayer pressure-area isotherm P(A)~(A-A_0)^{-n}. The crossover manifests itself in the transition from n=5/3 to n=3. Our microscopic model represents a single lipid molecule as a worm-like chain with finite irreducible cross-section area A_0, flexural rigidity K and stretching modulus Q in a parabolic potential with self-consistent curvature B(A) formed by entropic interactions between hydrocarbon chains in the lipid layer. The crossover area per lipid A* obeys relation Q^2/(KB(A*))~1 . We predict a peculiar possibility to deduce effective elastic moduli K and Q of the individual hydrocarbon chain from the analysis of the isotherm possessing such crossover. Also calculated is crossover-related behavior of the area compressibility modulus K_a, equilibrium area per lipid A_t, and chain order parameter S.

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I. N. Krivonos, S. I. Mukhin. 2007-06-21. Flexible-to-semiflexible chain crossover on the pressure-area isotherm of lipid bilayer. https://doi.org/10.1007/s11447-008-1011-6

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