Phosphatidylserine (PS) lipids are important signaling molecules and the most com-
mon negatively charged lipids in eukaryotic membranes. The signaling can be often
regulated by calcium, but its interactions with PS headgroups are not fully understood.
Classical molecular dynamics (MD) simulations can potentially give detailed descrip-
tion of lipid-ion interactions, but the results strongly depend on the used force eld.
Here, we apply the electronic continuum correction (ECC) to the Amber Lipid17 pa-
rameters of 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) lipid to improve
its interactions with Na+ and Ca2+ ions. The partial charges of headgroup, glycerol
backbone and carbonyls of POPS, bearing a unit negative charge, were scaled with a
factor of 0.75, derived for monovalent ions and the Lennard-Jones  parameters of the
same segments were scaled with a factor of 0.89. The resulting ECC-POPS model gives
more realistic interactions with Na+ and Ca2+ cations than the original Amber Lipid17
parameters, when validated using headgroup order parameters and electrometer con-
cept. In ECC-lipids simulations, Ca2+ cations do not simultaneously interact with
more than two PS lipids, and interactions with carboxylate groups is twice more likely
than with phosphate groups, while interaction with carbonyls is almost negligible. Our
results pave the way for more realistic MD simulations of anionic biological membranes
and demonstrate the usefulness of ECC also to charged lipids.