For both DPPC and POPC, simulations were performed with TIPS3P, 27 the 4-point OPC, and TIP4/05 long, and the first 100 ns were omitted from the analyses, based on the convergence analyses from our recent monolayer work. The equations of motion were integrated with a leap-frog integrator and with a time step of 2 fs. We used bu↵ered Verlet lists to keep track of atomic neighbours. The smooth PME and LJ-PME approaches were used to evaluate the long-range electrostatic and van der Waals interactions. The temperatures of the lipid and the solvent were coupled separately to a Nosé-Hoover thermostat with a time constant of 1 ps. P-LINCS was used to constrain bonds involving hydrogen atoms. The geometric combination rules were used for LJ-PME, in line with the CHARMM implementation of C36/LJ-PME. The surface pressure of the monolayer ⇧ at an area per lipid of APL was extracted from the surface tensions of the pure water-air interface ( 0 ) and the lipid monolayer-coated water-air interface ( (APL)) as