Training and Validation of a Liquid-Crystalline Phospholipid Bilayer Force Field

We present a united-atom model (gb-fb15) for the molecular dynamics simulation of hydrated liquid-crystalline dipalmitoylphosphatidylcholine (DPPC) phospholipid bilayers. This model was constructed through the parameter-space minimization of a regularized least-squares objective function via the ForceBalance method. The objective function was computed using a training set of experimental bilayer area per lipid and deuterium order parameter. This model was validated by comparison to experimental volume per lipid, X-ray scattering form factor, thermal area expansivity, area compressibility modulus, and lipid lateral diffusion coefficient. These comparisons demonstrate that gb-fb15 is robust to temperature variation and an improvement over the original model for both the training and validation properties.