Aqueous citrate: a first-principles and force-field molecular dynamics study

Great advances have been made in the fields of biomolecular and bio-interfacial simulation in recent years. One of the current limitations of such studies when modeling these systems, however, is the lack of suitable, published force-fields for citrate; an anion often present either as a buffering agent, eluent or nanoparticle capping ligand. Here we develop a force-field for citrate using data from first-principles simulations carried out under aqueous conditions. Our force-field is further validated against electronic structure theory calculations carried out at the MP2/6-31G* level of theory. Extended force-field-based molecular dynamics simulations of citrate in solution, using our new force-field parameters, offer a unique insight into the influence of co-ordinating Na+ counterions on the aqueous structure of citrate.