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Adsorption of the cysteine–tryptophan dipeptide at the Au(110)/liquid interface studied using reflection anisotropy spectroscopy

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  • Blasco Morozzo della Rocca, Department of Biology, University of Rome Tor Vergata, Rome, 00133, Italy, Italy
  • C I Smith, Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom, United Kingdom
  • Cinzia Tesauro
  • Alessandro Desideri, *Department of Biology, University of Rome Tor Vergata, Via Della Ricerca Scientifica, Rome 00133, Italy., Denmark
  • P Weightman, Department of Physics, Oliver Lodge Laboratory, University of Liverpool, Liverpool, L69 7ZE, United Kingdom, United Kingdom
  • Department of Molecular Biology
The adsorption of a cysteine–tryptophan dipeptide has been monitored at a Au(110)/electrolyte interface using reflection anisotropy spectroscopy. At −0.6 V the dipeptide adsorbed through the formation of Au–S bonds and a link between the NH2 group at the Au surface. As the applied potential was changed to + 0.6 V the NH2 group left the surface and the spectra suggest that two dipeptides form a disulphide bridge that binds to the Au surface. This event is accompanied by changes in the orientation of, and possibly interactions between, tryptophan moieties. Returning the applied potential to −0.6 V failed to re-establish the initial population of Au–S bonds and the changes induced in the region of the spectrum associated with the tryptophan's by the positive potentials were permanent on the time scale of an hour. Subtle changes associated with the tryptophan moieties indicate that the orientation of the tryptophans is very sensitive to the applied potential. Cycling of the potential showed a stable inter-conversion between Au–S bonds and Au–disulphide bonds at low scan rates, but at higher scan rates not all the broken disulphide bonds were able to reform. Irreversible changes were also observed in the tryptophan region of the spectrum during potential cycling.
Original languageEnglish
JournalSurface Science
Volume604
Issue23-24
Pages (from-to)2170-2176
Number of pages6
ISSN0039-6028
DOIs
Publication statusPublished - 2010

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