Computational Calorimetry with the MARTINI Force Field

The goal of this work is to validate the MARTINI simulation model for lipids by pinpointing the gel to fluid phase transition temperature of DPPC:cholesterol mixtures. A ``computational calorimetry'' analysis was applied to a large set of molecular dynamics simulation data ranging from 5{\%} to 30 mol {\%} cholesterol. Computational calorimetry mimics calorimetry as performed in laboratory experiments, obtaining the heat capacity as a function of temperature, and therefore admits a direct comparison to a large body of experimental literature on the same mixtures. Other observables such as the area per lipid, the thickness of the bilayer, and the ordering of the lipid tails are also reported. The simulated results agree qualitatively with the experimental results, including the shift in transition temperature with increasing cholesterol content.