A DFT study of the [Cu2+-(GlyGlyHis - 3H+)]−1 ion complex structure

Conformations of Cu2+ ion binding to GlyGlyHis (GGH) tripeptide, a model compound for human serum albumin where the Cu2+ binding site is the N-terminal AspAlaHis, have been studied by many research groups. The specific interactions between GGH and Cu2+ ion, which is known to form a [Cu2+-(GlyGlyHis - 3H+)]−1 planar structure in aqueous solution, are studied in terms of optimized structures and energies in B3LYP/6-311+G(d,p) calculations. Five geometries are tried to optimize the [Cu2+-(GlyGlyHis - 3H+)]-1 planar structures. A Cu2+-NNNN planar structure involved the four coordination of a terminal amino nitrogen, two deprotonated amide nitrogens, and an imidazole-N3 atom at the deprotonated imidazole ring, has been calculated to be the most stable structure among the [Cu2+-(GlyGlyHis - 3H+)]−1 complexes. The energy and geometry of the Cu2+-NNNO coordination structure involving a C-terminal carboxyl oxygen are also calculated to understand the NNNN-coordination preference of Cu2+ in the [Cu2+-(GlyGlyHis - 3H+)]-1 complex.