To further investigate behavior of ions in OPLS3e we scaled the charge of monovalent NaCl and divalent CaCl 2 by factor 0.75, as in ECC theory, and performed simulations using 1000 mM concentrations with scaled charges. Scaling enhanced order parameters for the alpha and beta carbons in the presence of additional 1000 mM NaCl (Fig. ) but was not sufficient for CaCl 2 (Fig. ). However, with scaled charged of CaCl 2 , ion binding to membrane equilibrates much faster than with unscaled charges (Fig. ) The over binding of Ca 2+ cannot be easily fixed by scaling the charge of the ions (or by adding non-bonded fix parameters). To this end, Melcr et al. extended the ECC theory to include also partial charges of the polar region of POPC phospholipids to build the ECC-POPC model based on the Lipid14 force field (they also did this for CHARMM36 with same scaling) . The resulting ECC-POPC model produces experimental order parameter responses to NaCl and even for divalent CaCl 2 unlike any other current force field, and can thus be considered as one of the most realistic models to describe POPC lipid membrane in the presence of ions so far.