Analytical derivation of thermodynamic properties of bilayer membrane with interdigitation |
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Authors: | S I Mukhin B B Kheyfets |
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Institution: | 1.Department of Theoretical Physics and Quantum Calculations,State University of Technology and Science MISA,Moscow,Russia;2.Physical Chemistry Department,State University of Technology and Science MISA,Moscow,Russia |
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Abstract: | We consider a model of bilayer lipid membrane with interdigitation, in which the lipid tails of the opposite monolayers interpenetrate.
The interdigitation is modeled by linking tails of the hydrophobic chains in the opposite monolayers within bilayer as a first
approximation. This model corresponds to the types of interdigitation that are not related with the areal “hydrophobic” dilation
of the membrane. A number of essential thermodynamical characteristics are calculated analytically and compared with the ones
of a regular bilayer membrane without interdigitation. Important difference between lateral pressure profiles at the layers
interface for linked and regular bilayer models is found. In the linked case, the lateral pressure mid-plane peak disappears,
while the entropy decreases and the free energy per chain increases. Within our model we found that in case of elongation
of the chains inside a nucleus of, e.g., liquid-condensed phase, homogeneous interdigitation would be more costly for the
membrane’s free energy than energy of the hydrophobic mismatch between the elongated chains and the liquid-expanded surrounding.
Nonetheless, an inhomogeneous interdigitation along the nucleus boundary may occur inside a “belt” of a width that varies
approximately with the hydrophobic mismatch amplitude. |
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