Structural investigation of a chiral adsorbate: α-alanine on Cu(110)

The manner in which biologically active molecules, such as proteins, peptides, etc. bind to surfaces is of relevance due to a number of applications such as the development of biosensors and biocompatible materials. The structure, conformation and local order of these molecules upon adsorption influence their interaction with further incoming species and the process of molecular recognition. Many of these complex molecules are made up mainly of α-amino acids (in which the amino group, NH2, is bonded to the so called α-carbon; see description in the following section). Therefore the usual surface science approach to understand their essential interaction with inorganic surfaces has been initially to study model systems consisting of these smaller units adsorbed on metal surfaces. However, and in spite of the interest of these biological molecules and the growing importance of the technologies based on them, only a few α-amino acid/metal systems have been investigated so far. Most of these studies have been devoted to the adsorption of glycine (NH2CH2COOH) on Cu surfaces. Glycine is not only the simplest of the α-amino acids but also the only one that is non-chiral . Therefore, the natural step forward in this bottom-up approach would be to study the adsorption of the simplest chiral amino acid, alanine (NH2CHCH3COOH). Moreover, the study of the adsorption structure of chiral substances on surfaces is significant for heterogeneous enantioselective catalysis. This kind of catalysis is based on the use of chiral substances as modifiers of conventional metallic catalysts to achieve what is called enantioselectivity, that is, to attain catalytic production of pure enantiomeric forms (or enantiomers) of a certain molecule. This is important in particular for the pharmaceutical industry. The reason for this is that most of the pharmaceutical drugs are chiral, and opposite enantiomers of the same substance interact quite differently with