Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 56: Metal substrates: Adsorption of organic / bio molecules III

O 56.3: Talk

Wednesday, March 28, 2012, 17:15–17:30, A 053

Cysteine on Ag(111) – Chiral self-assembly and temperature-dependant phase-transitions — •Sybille Fischer¹, Anthoula C. Papageorgiou¹, Matthias Marschall¹, Joachim Reichert¹, Katharina Diller¹, Florian Klappenberger¹, Francesco Allegretti¹, Alexei Nefedov², Christof Wöll², and Johannes V. Barth¹ — ¹Physik Department E20, Technische Universität München, 85748 Garching, Germany — ²Institut für Funktionelle Grenzflächen, Karlsruher Institut für Technologie, Hermann-von-Helmholtz-Platz, 76344 Eggenstein-Leopoldshafen, Germany

Understanding the interactions between the chiral amino acid cysteine and metal surfaces is an important step towards creating tailored biofunctionalized surfaces using the molecule’s chemical functionalities and medical properties. L-cysteine is involved in the pathogenetic mechanism of HIV [1] as well as in metal interaction centers of many proteins [2]. Being the only proteinogenic amino acid containing a thiol group, cysteine is also used to anchor longer peptides on metal surfaces.

Here a combined STM and XPS study on cysteine is presented. STM measurements at room temperature were carried out on both enantiopure cyteine compounds showing distinctive self-assembly patterns. A phase transformation was discovered after annealing to 400 K. XPS was employed to elucidate the driving force of this transformation. A strong chemical shift of the nitrogen 1s core level revealed a concomitant change of the molecule from a zwitterionic to an anionic state.

[1] Eck, H.-P. et al, Biol. Chem. Hoppe-Seyler 1989, 370, 101–108

[2] Barnham, K.J. et al, Nat. Rev. Drug Discovery 2004, 3, 205–214