Adsorption Structure of Glycyl-Glycine on Cu(110)

Multilayer, monolayer, and submonolayer films of the dipeptide glycyl-glycine on the Cu(110) surface have been studied by a combination of soft X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and density functional theory calculations. Detailed models of the electronic structure and adsorption geometry at each coverage have been proposed. After adsorption, the molecules bind to the copper surface in two forms, zwitterionic and anionic, and the latter is dominant after annealing. In the monolayer, the anionic form of the dipeptide coordinates to the surface via the oxygen atoms of the carboxylate or peptide group and amino nitrogen atom, whereas in the submonolayer regime, the amino group interacts with the surface through a hydrogen atom.