Structures and Bonding Properties of Gold-Arg-Cys Complexes: DFT Study of Simple Peptide-Coated Metal

Abstract

We present the structures, bonding characteristics, and infrared spectra of the gold surface (111)-Arg-Cys (Arg-Cys@Au(111)) complex calculated by a periodic plane wave DFT technique. We examine the detailed features of bonding between the gold surface and dipeptide. The dipeptide is revealed to form a covalent bond via the -SH group with 2-3 gold atoms, and also weak noncovalent interactions via the carboxyl and guanidine side chain lying more or less parallel to the gold surface. The S-H bond dissociates as a result of the S--(Au)(n) bond formation, with the hydrogen atom binding to the guanidine moiety. The acidic proton stays at the carboxyl group in the most stable structure of Arg-Cys@Au(111). The calculated infrared spectra are compared with experimental observations reported by Petoral and Uvdal (Colloids Surf., B 2002, 25, 335).