FIGURE 1.

Equilibrium configuration of a complex consisting of two bilayer membranes, each with 390 lipids and five DNA strands. The lipids are modeled as trimers with hydrophilic (black) and hydrophobic (gray) particles. The DNA (red) are modeled as rigid rods with a uniform negative axial charge density. The complex is isoelectric, i.e., the negative charge of the DNA is neutralized by the charge of the cationic lipids with no added salt. Thus, each bilayer in the shown complex includes 150 monovalent lipids, all of which reside in the inner layers facing the DNA array. Each DNA rod carries a total charge of −60 e.