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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. Barth11Physik 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

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