Molecular dynamics investigation of dipeptide-transition metal salts in aqueous solutions

Molecular dynamics (MD) simulations of glycylglycine dipeptide with transition metal ions (Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+)) in aqueous solutions have been carried out to get an insight into the solvation structure, intermolecular interactions, and salt effects in these systems. The solvation structure and hydrogen bonding were described in terms of radial distribution function (RDF) and spatial distribution function (SDF). The dynamical properties of the solvation structure were also analyzed in terms of diffusion and residence times. The simulation results show the presence of a well-defined first hydration shell around the dipeptide, with water molecules forming hydrogen bonds to the polar groups of the dipeptide. This shell is, however, affected by the strong electric field of divalent metal ions, which at higher ion concentrations lead to the shift in the dipeptide-water RDFs. Higher salt concentrations lead also to increased residence times and slower diffusion rates. In general, smaller ions (Cu(2+), Zn(2+)) demonstrate stronger binding to dipeptide than the larger ones (Fe(2+), Mn(2+)). Simulations do not show any stronger association of peptide molecules indicating their dissolution in water. The above results may be of potential interest to future researchers on these molecular interactions.