Free energy of WALP23 dimer association in DMPC, DPPC, and DOPC bilayers

► We present extensive potential of mean force calculations on helix-helix association. ► Helix-helix association for WALP23 peptides is favorable in DMPC, DPPC, and DOPC lipids. ► Association is most favorable in DMPC, with the largest positive hydrophobic mismatch. ► In the MARTINI simulations, only association in DMPC has a favorable entropy change. ► We introduce new analysis programs for membrane perturbation.