Slight overestimation of sodium binding compared to the minimal binding suggested by experimental data. On the contrary, responses to CaCl 2 differ in our MD simulation between OPLS3e and CHARMM36. OPLS3e produces qualitatively right response to rising CaCl 2 concentration, but radically overestimates the Ca 2+ binding. Response of CHARMM36 seem to be closer to the experiments, although it is not able to reproduce the difference between Na + and Ca 2+