Confirmation of Initial Stable Adsorption Structures of Leucine and Tyrosine Adsorbed on a Cu(110) Surface

The structures and stability levels of leucine (Leu) and tyrosine (Tyr) adsorbed on a Cu(110) surface, at initial levels of coverage (less than 0.25 monolayer), were investigated using reflection–absorption infrared spectroscopy and high-resolution photoemission spectroscopy (HRPES), as well as by performing density functional theory calculations. At an initial coverage, the O–H dissociation bonded structure was indicated from the spectral results to be the most favorable structure for Leu adsorbed on the Cu(110) surface, whereas the O–H dissociated-N dative bonded structure was most favorable for adsorbed Tyr. These models were further supported by the results of experiments, in which the systems were exposed to other molecules and HRPES was used to monitor whether the amine or carboxylic groups of the adsorbed amino acids became reactive.