Construction and molecular modeling of phospholipid surfaces

A protocol is given for the construction of phospholipid surfaces that possess variable head groups and thus variable net charge. Ab initio quantum mechanical calculations are performed to establish the necessary force field (AMBER) parameters. The charge distribution is defined by an electrostatic potential method consistent with the ab initio wave function. As a model calculation, a monolayer surface with head groups of phosphatidylserine and phosphatidylcholine derived from the crystal structure of 1,2‐dilauroyl‐DL‐phosphatidylethanolamine (DLPE) is placed in a water bath with two Ca(II) ions present. The resultant surface is energy‐optimized followed by 64 ps of molecular dynamics integration. Evaluation of calcium ion coordination environments, characterization of the P‐N dipole inclination with respect ot the plane of the monolayer, and calculation of molecular surface area is performed and compared with experimental data.