We ran 500-ns simulations (1 000 ns for OPLS4 POPC at 5 w/l) using the OPLS4 The POPC starting structures were created with the system builder and model system regeneration tools within the software. The standard DMPC starting structures for Desmond were found to be improper due to random chirality; they were recreated on our request by the Schrödinger technical support in March 2024 and fixed for the 2024-2 release. The SPC water model was used for solvation. Dehydrated systems were derived from the fully hydrated membranes by removing excess water. Default Desmond settings for membrane systems (with 2-fs time step and 10-ps saving frequency) were used, and the pre-simulation relaxations done using the default membrane relaxation protocol. Temperature was set to 300 K for POPC and 314 K for DMPC. Systems were kept in the NPT ensemble with the semi-isotropic (xy coupled separately from z) Martyna-Tobias-Klein barostat and the Nosé-Hoover-chain thermostat. The default Ewald electrostatics were used. For analysis, the Desmond output files were converted into GROMACS trajectories and topology files with VMD version 1.9.3. Simulations using CHARMM36 were run with GROMACS versions 2019.5 or 2022.4. CHARMM-GUI Membrane Builder (charmmgui.org) was used to create the systems; the force field parameters were obtained from its outputs. The CHARMM TIP3P water model was used for solvation. Dehydrated systems were derived from the fully hydrated membranes by removing excess water. Simulations were performed with a 2-fs time step and data saved every 10 ps. Temperature was set to 300 K for POPC and 314 K for DMPC. Systems were kept in the NPT ensemble with the semi-isotropic (xy coupled separately from z) Parrinello-Rahman barostat and the Nosé-Hoover thermostat. Particle Mesh Ewald (PME) was used for electrostatics.