First-principles study of the adsorption of lysine on hydroxyapatite (1 0 0) surface

The adsorption of lysine (Lys) on hydroxyapatite (HA) (1 0 0) surface was studied using density functional theory calculations within the generalized gradient approximation framework. The optimal adsorption pattern was identified from a number of interactive Lys-HA structures. The carbonyl-O, amine-H and Cɛ-H atoms are active sites in Lys that interact directly with the Ca ion and phosphate-O atoms on the HA (1 0 0) surface, respectively. Multiple interactions were noted between Lys and HA surface. The adsorption is mainly stabilized by the CaO ionic bonding, followed by hydrogen bond and/or van der Waals interaction between phosphate-O and Lys-HA. Both the Lys and HA surface structures are subjected to some changes upon adsorption. The zwitterionic form of Lys was found more stable on the HA (1 0 0) surface than its neutral form. Our calculations reveal the structural characteristics and their variations for the Lys-HA systems, which are essential for understanding the interaction mechanism of biomolecules with inorganic biomaterials.

Highlights► Conformers of Lys on HA (1 0 0) surface are identified. ► Multiple interactions that favor the Lys adsorption are revealed. ► Strong ionic bonding is formed between carbonyl-O in Lys and Ca ion on HA surface. ► Both Lys and HA structures are subjected to changes upon adsorption.