title: Hysteresis and the Cholesterol Dependent Phase Transition in Binary Lipid Mixtures with the Martini Model.
abstract: Extensive Martini simulation data, totaling 5 ms, is presented for binary mixtures of dipalmitoylphosphatidylcholine (DPPC) and cholesterol. Using simulation initiated from both gel (so) and liquid-disordered (Ld) phases, significant and strongly cholesterol-dependent hysteresis in the enthalpy as a function of temperature is observed for cholesterol mole fractions from 0 to 20 mol %. Although the precise phase transition temperature cannot be determined due to the hysteresis, the data are consistent with a first order gel to fluid transition, which increases in temperature with cholesterol. At 30 mol % cholesterol, no hysteresis is observed, and there is no evidence for a continuous transition, in either structural parameters like the area per lipid or in the heat capacity as a function of temperature. The results are consistent with a single uniform phase above a critical cholesterol composition between 20 and 30 mol % in Martini, while highlighting the importance and difficulty of obtaining the equilibrium averages to locate phase boundaries precisely in computational models of lipid bilayers.
authors.affiliation: Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Clement
authors.initials: C
authors.lastname: Arnarez
authors.affiliation: Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Alexis
authors.initials: A
authors.lastname: Webb
authors.affiliation: Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Rouvière
authors.affiliation: Department of Physics and Astronomy, University of Delaware , Newark, Delaware 19716, United States.|Department of Chemistry and Biochemistry, University of Delaware , Newark, Delaware 19716, United States.
authors.forename: Edward
authors.identifier: 0000-0003-4590-0363
authors.initials: E
authors.lastname: Lyman
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry*; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D044367:Phase Transition; D013696:Temperature; D013816:Thermodynamics
chemical_list: D008051:Lipid Bilayers; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol