Understanding the Phase Changes of Coarse-Grained Model Bilayers Through Computational Calorimetry

In this study, we assess the thermodynamic behavior of a variety of coarse-grained lipid bilayer models across the temperature range which experimentally produces the gel phase, the ripple phase, and the liquid crystalline phase. Computational model systems including both lipids and water are often validated by comparison to structural or thermodynamic data at ambient conditions or by comparison to the variation of structural data as a function of temperature. Here we compare these models on new grounds by using a computational version of differential scanning calorimetry, an experimental technique widely employed to observe phase transitions in model bilayer systems. The goal of such an endeavor is to gain insight into the driving forces behind phase changes in single component model lipid systems. The strong interest in the phase behavior of multi-component bilayers as simple models of cell membranes requires that we also more deeply understand the phase behavior of the pure lipid bilayer computational models first. This study yields progress in understand the driving forces of each model and the trade-offs in choosing various coarse-grained models.