To clarify if water model has an impact on cation binding affinity of membranes in OPLS3e, we performed simulations using TIP3P water model instead of SPC with 1000 mM concentration of NaCl or CaCl 2 and without ions. Without ions (Fig. ) and at 1000 mM concentrations (Fig. ) TIP3P produced similar order parameters as SPC, suggesting that there is no major difference between SPC and TIP3P water models in OPLS3e with or without ions.