Pressures profiles can be computed with NAMD, but have not been implemented into the GPU-resident algorithms, requiring separate simulations on CPUs. As with the equilibrium simulations, the pressure profile simulation used CHARMM36 force field for lipids with anisotropic pressure coupling and 2 fs timesteps maintained at 310K. For consistency with older work, the long-range non-bonded Lennard Jones (LJ) cutoff was set to 18 Å . The pressure profile for both the cis and trans membrane system is calculated by slicing the simulation box into 92 slices of about 1 Å thickness in z or the normal axis, and calculating the local pressure tensor using the formulation given by Lindahl and Edholm 45 as implemented in NAMD2.14. In molecular simulation, the pressure profile can be converted to surface tension (γ) by calculating the difference between normal [P N = P zz ] and lateral [P L = (P xx + P yy )/2] components by: 44,45