Open AccessHysteresis and the Cholesterol Dependent Phase Transition in Binary Lipid Mixtures with the Martini Model
Author(s) -
Clément Arnarez,
Alexis Webb,
Eric Rouvière,
Edward Lyman
Publication year - 2016
Publication title -
the journal of physical chemistry. b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 392
eISSN - 1520-6106
pISSN - 1520-5207
DOI - 10.1021/acs.jpcb.6b09728
Subject(s) - dipalmitoylphosphatidylcholine , hysteresis , thermodynamics , phase transition , cholesterol , enthalpy , chemistry , phase (matter) , transition temperature , materials science , membrane , organic chemistry , phospholipid , biochemistry , physics , condensed matter physics , phosphatidylcholine , superconductivity
Extensive Martini simulation data, totaling 5 ms, is presented for binary mixtures of dipalmitoylphosphatidylcholine (DPPC) and cholesterol. Using simulation initiated from both gel (s o ) and liquid-disordered (L d ) 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.