DFT study of cyclic glycine-alanine dipeptide binding to gold nanoclusters

Abstract

In this work, we studied the interactions between cyclic glycine-alanine dipeptide c(GA) and gold nanoclusters (AunNCs, where n = 2–10) using density functional theory (DFT), atoms-in-molecules theory (AIM), and natural bond orbital analysis (NBO). This dipeptide (DP) consists of two amino acid residues (glycine and alanine); thus, the preference of both residues for binding to gold atoms was examined. The preference of alanine residue to the studied AunNCs was found to be greater than that of glycine residue. Two types of interactions were exhibited between the AunNCs and c(GA), the partially-covalent partially-electrostatic type and electrostatic interaction. Performance of two DFT functionals and different basis sets is assessed. The results benchmark the importance of the DFT functional with dispersion and long-range corrections, as well as the polarization functions in the basis sets for the gold lusters-peptide binding. The binding energy (ΔEbind) values of the c(GA)−AunNCs complexes in gas and water implicit solvent were compared with those previously published for cyclic glycine-glycine DP−AunNCs complexes. It was found that the ΔEbind values of the former complexes are greater than those of latter ones in water solvent.