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Issue 6, 2016
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Coarse-grained molecular simulations of the melting kinetics of small unilamellar vesicles

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Abstract

Simulations of small unilamellar lipid bilayer vesicles have been performed to model their response to an instantaneous rise in temperature, starting from an initial low-temperature structure, to temperatures near or above the main chain transition temperature. The MARTINI coarse-grained force-field was used to construct slabs of gel-phase DPPC bilayers, which were assembled into truncated icosahedral structures containing 13 165 or 31 021 lipids. Equilibration at 280 K produced structures with several (5–8) domains, characterized by facets of lipids packed in the gel phase connected by disordered ridges. Instantaneous heating to final temperatures ranging from 290 K to 310 K led to partial or total melting over 500 ns trajectories, accompanied by changes in vesicle shape and the sizes and arrangements of remaining gel-phase domains. At temperatures that produced partial melting, the gel-phase lipid content of the vesicles followed an exponential decay, similar in form and timescale to the sub-microsecond phase of melting kinetics observed in recent ultrafast IR temperature-jump experiments. The changing rate of melting appears to be the outcome of a number of competing contributions, but changes in curvature stress arising from the expansion of the bilayer area upon melting are a major factor. The simulations give a more detailed picture of the changes that occur in frozen vesicles following a temperature jump, which will be of use for the interpretation of temperature-jump experiments on vesicles.

Graphical abstract: Coarse-grained molecular simulations of the melting kinetics of small unilamellar vesicles

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Publication details

The article was received on 15 Oct 2015, accepted on 15 Dec 2015 and first published on 15 Dec 2015


Article type: Paper
DOI: 10.1039/C5SM02560E
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Soft Matter, 2016,12, 1765-1777

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    Coarse-grained molecular simulations of the melting kinetics of small unilamellar vesicles

    L. A. Patel and J. T. Kindt, Soft Matter, 2016, 12, 1765
    DOI: 10.1039/C5SM02560E

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