Conformational study of methylphosphocholine: a prototype for phospholipid headgroups in membranes

Phospholipid bilayers constitute the largest structural component of cell membranes, in which choline phospholipids are abundant. In this study, through a theoretical sampling on a methylphosphocholine (MePC) potential energy surface, a set of conformers was selected as a prototype for the membrane phospholipid head. We performed a detailed conformational study of such a prototype, both as an isolated moiety and in a solvated system. We used the polarizable continuum model (PCM) to account for solvation effects. We used a quantum-mechanical methodology based on density functional theory (DFT) and the 6-31G(d,p) basis set for the calculations. Through this methodology we were able to obtain a set of conformations that presented a mirror-image pattern, in good agreement with the experimental geometric values for the different phosphocholine derivatives. Potential curves for the main parameters of the dihedral space of MePC were obtained and are provided to guide future force-field parameterizations.