Electrospray ion beam deposition of small peptides on solid surfaces: A molecular level description of the glutathione/copper interface

Abstract

Herein, we investigate the adsorption behavior of Glu-Cys-Gly peptide on copper surfaces under ultra-high vacuum condition by exploring the electrospray - ion beam deposition (ES-IBD) method. ES-IBD combines an atmospheric pressure ionization source and a vacuum deposition technique, which allows bio-organic molecules to adsorb at their intact state. We use a multi-technique UHV chambers in which ES-IBD and surface characterizations are performed in adjacent compartments, namely PM-IRRAS and XPS. Results show that peptides preserve their molecular structure in the adsorbed state, and their binding mechanisms are highly impacted by the copper crystal face. DFT calculations are performed to identify the most stable configurations of the peptide in the adsorbed state, and core level shifts calculations are compared to experimental XPS data. The molecule adsorbs intact in a deprotonated state for both surfaces. On Cu(111) face, the deprotonated thiol group adsorbs in a single chemical environment, resulting in only one S 2p binding energy, while it shows two binding energies on the Cu(110) face. In addition, N 1s binding energies are not all equal, one −NH2 having a lower binding energy, compared to that observed on Cu(1 1 1), due to the formation of a H-bond with the Cu surface.