Dear Gromacs Users, I am trying to simulate a protein in lipid bilayer with a barium ion binding pocket in it, with Charmm27 FF in gromacs 4.5.4. I found that barium ion is not included under charmm27 ff ions.itp. I was wondering if there is any way to simulate protein with barium bound using gromacs and charmm27 ff? Thanks Pramod