The systems containing a double bilayer structure (double bilayer, interdigitated) were equilibrated using an isothermal-isobaric (NPT) ensemble at 288 K (15°C) and 1 bar by restraining the lipids from their primary hydroxyl oxygen O1 (see Figure for atom numbering) with a harmonic force constant of 200 kJ mol -1 nm -2 for 1 ns with a 1 fs timestep.