Figure 9.

Charge distributions of headgroup atoms and water oxygens over the trajectory. O1 and O2, refer to the bridging phosphate oxygens; O3 and O4 refer to the equivalent double-bonded phosphate oxygens; O-N refers to water oxygens associated with headgroup nitrogen atoms; and O-P refers to water oxygens associated with headgroup phosphorus atoms. The corresponding charges in the fixed-charge CHARMM force field (dotted lines), as well as the MP2/cc-pVTZ charges for the headgroup atoms included in the parameterization (dashed lines), are also shown.