  Ionic liquids (ILs) constitute one of the most active fields of research
nowadays. Many organic and inorganic molecules can be converted into ions via
relatively simple procedures. These ions can be combined into ILs. Amino acid
based ILs (AAILs) represent a specific interest due to solubilization of
biological species, participation in enzymatic catalysis, and capturing toxic
gases. We develop a new force field (FF) for the seven selected AAILs
comprising 1-ethyl-3-methylimidazolium cation and amino acid anions with polar
residues. The anions were obtained via deprotonation of carboxyl group. We
account for peculiar interactions between the anion and the cation by fitting
electrostatic potential for an ion pair, in contrast to isolated ions. The van
der Waals interactions were transferred from the CHARMM36 FF with minor
modifications, as suggested by hybrid density functional theory. Compatibility
between our parameters and CHARMM36 parameters is preserved. The developed
interaction model fosters computational investigation of ionic liquids.
