Several strategies to fix the over binding of ions to membranes have been proposed in the literature. Nbfix, which was used for CHARMM36 in this study, addresses the issue by tuning non-bonded parameters for specific atom pairs separately instead of using the standard arithmetic combining rule . Another alternative solution is the electronic continuum correction (ECC) strategy which takes electronic polarization effects of solvent into account by scaling the charge of the ions . We tested a similar scaling as in the ECC model for NaCl and CaCl 2 in OPLS3e, which pre-scaling to overestimates Na + and Ca 2+ binding to membrane (Fig 5 .). Scaling of 0.75 for Na + and Cl -ions decreased Na + binding to membrane, and order parameters were closer to experimental values than without scaling (SI Fig. ). For CaCl 2 , the similar simple scaling of ionic charges did not fix the surplus ion binding to the membrane (SI Figs and). In ECC-POPC model ( ) scaling of both ions and partial charges of lipid head group atoms was conducted resulting in one of the most realistic force fields for lipids so far, since it can produce accurate binding also for divalent Ca 2+ which, as already previously stated, has been very challenging with all current force fields.