Predictions of Phase Separation in Three-Component Lipid Membranes by the MARTINI Force Field

Ryan S. Davis, P. B. Sunil Kumar, Maria Maddalena Sperotto, Mohamed Laradji

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The phase behavior of the coarse-grained MARTINI model for three-component lipid bilayers composed of dipalmytoyl-phosphatidylcholine (DPPC), cholesterol (Chol), and an unsaturated phosphatidylcholine (PC) was systematically investigated by molecular dynamics simulations. The aim of this study is to understand which types of unsaturated PC induce the formation of thermodynamically stable coexisting phases when added to mixtures of DPPC and Chol and to unravel the mechanisms that drive phase separation in such three-component mixtures. Our simulations indicate that the currently used MARTINI force field does not induce such phase separation in mixtures of DPPC, Chol, and unsaturated PCs with a low unsaturation level, such as palmitoyl-oleoyl-phosphatidylcholine (POPC) or dioleoyl-phosphatidylcholine (DOPC). Also, we found that phase separation does occur in mixtures of DPPC, Chol, and polyunsaturated PCs, such as dilinoleyl-phosphatidylcholine (DUPC) and diarachidonoyl-phosphatidylcholine (DAPC). Through systematic tweaking of the interactions between the hydrophobic groups of the PC molecules, we show that the appearance of phase separation in three-component lipid bilayers, as modeled through the MARTINI force field, is primarily due to the interactions between the coarse-grained molecules, i.e., the beads, rather than due to the differences between the conformations of saturated and unsaturated lipid acyl chains, namely entropy driven.
    Original languageEnglish
    JournalJournal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
    Volume117
    Issue number15
    Pages (from-to)4072-4080
    ISSN1520-6106
    DOIs
    Publication statusPublished - 2013

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