The membranes were equilibrated with the following four-step-scheme: 1) 50 ps with a 1 fs timestep and using a canonical (NVT) ensemble at 348 K (75°C) without position restraints, 2) 10 ns with 2 fs timestep continuing in NVT conditions at the same temperature, but now with 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 , 3) 10 ns with a 2 fs timestep using a NPT ensemble with 1 bar pressure using the same temperature and position restraints as in the previous step, and 4) simulated annealing from 348 K to 288 K over 60 ns (equating to a cooling rate of 1 K/ns) in NPT conditions without position constraints.