Figure 1.

(a) Diagram of the units over which charge is constrained in the charge-equilibration model for DMPC. Units 1 and 2 are analogous to the model compounds TMA and DMP, respectively. Units 3 and 4, the acyl parts, were previously parameterized (52) and were not included in this parameterization. Units 5–8 are analogous to hexane, which was previously parameterized (75). (b) The model compound o-phosphorylcholine, used to fit the N-C-C-O and C-C-O-P torsional parameters of DMPC.