Difference in the Conformation and Dynamics of Aspartic Acid on the Flat Regions, Step Edges, and Kinks of a Calcite Surface: A Molecular Dynamics Study

Abstract

Molecular dynamics simulations were conducted to investigate the conformation and dynamics of an aspartic acid molecule near the {104} and {110} planes of a CaCO3 calcite crystal, near the acute and obtuse [114] step edges on the {104} plane, and near kinks formed at the step edges. The simulations indicate that the amino acid binds indirectly to the {104} plane, whereas it binds directly to the {110} plane. The simulations also indicate that the acid binds directly to the acute step edge but does not bind to the obtuse step edge. These differences in the binding of the acid to the planes and the step edges were attributed to a difference in the structure of the surrounding water. The simulations also indicate that the acid binds to the kink formed at both the acute and the obtuse step edges, if a Ca2+ ion is placed at the corner of the kink. The binding was much stronger at the kink than at the planes and the step edges.