The coarse-grained models for DPPC and water. The CG model of the DPPC molecule is depicted in Figure . We adopt a general 3-to-1 mapping for the solvent water and the lipid tails, whereas the head group is modelled as 4 beads. The N bead represents the choline atoms N + (CH3)3-CH2, the phosphate group CH2-PO4 is represented by the P bead, and the glycerol backbone, CH2-CH(CH2-O-C=O)-O-C=O, including the carbonyl groups is represented by two G beads. The carbonyl carbons are included in the G beads since, they are not so hydrophobic due to the presence of the carbonyl oxygen. The remaining 15 alkyl groups in the tail, (CH2)14-CH3, are mapped into five beads: four C beads and one E bead at the end. This mapping results in a 14-bead representation of the DPPC molecule. The solvent water bead W represents 3 water molecules. The various interactions between the coarse-grained (CG) beads are parameterized using a systematic approach.