Do peptide nucleic acids form self-assembled monolayers on pyrite surfaces?

We have characterized the adsorption of thiol-modified peptide nucleic acid (PNA) molecules on a natural pyrite surface by means of X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) techniques. Whereas single stranded PNA forms partially-ordered self-assembled monolayers (SAMs) on gold surfaces, no preferential orientation of PNA is observed upon adsorption on pyrite (FeS2) surfaces. The N1(s) XPS core level peak of PNA has been decomposed in curve-components, and every component has been assigned to different chemical species. This analysis shows that in pyrite the PNA nucleobases interact with the iron from the surface rather than by the sulfur of the thiolated molecule.