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Experimental and theoretical Raman and surface‐enhanced Raman scattering study of cysteine

Guillermo Díaz FlemingMolecular and Atomic Spectroscopy Laboratory, Department of Chemistry, Faculty of Sciences, University of Playa Ancha, Casilla 34‐V, Valparaiso, ChileJustin J. FinnertyInstitute for Pure and Applied Chemistry and Center of Interface Science, University of Oldenburg, D‐26111 Oldenburg, GermanyM. Campos‐ValletteMolecular Spectroscopy Laboratory, Department of Chemistry, Faculty of Sciences, University of Chile, Casilla 653, Santiago, ChileFreddy CélisMolecular and Atomic Spectroscopy Laboratory, Department of Chemistry, Faculty of Sciences, University of Playa Ancha, Casilla 34‐V, Valparaiso, ChileÁlvaro AliagaMolecular Spectroscopy Laboratory, Department of Chemistry, Faculty of Sciences, University of Chile, Casilla 653, Santiago, ChileCarlos FredesMolecular and Atomic Spectroscopy Laboratory, Department of Chemistry, Faculty of Sciences, University of Playa Ancha, Casilla 34‐V, Valparaiso, ChileRainer KochInstitute for Pure and Applied Chemistry and Center of Interface Science, University of Oldenburg, D‐26111 Oldenburg, Germany

2009en

ABI

Annotatsiya

Abstract Raman spectra in solid and 1 M solution of L ‐cysteine and surface‐enhanced Raman scattering (SERS) spectra of this molecule in the zwitterionic form, by using colloidal silver nanoparticles, have been recorded. Density functional theory with the B3LYP functional was used for the optimizations of the ground state geometries and simulation of the vibrational spectrum of this amino acid. The SERS spectrum with a large silver cluster as a model metallic surface was simulated for the first time. Taking into account the experimental and calculated Raman and SERS vibrations and the corresponding assignments, as well as a comparison of force constants and geometrical parameters between the free zwitterion cysteine and the one in the presence of the colloidal silver nanoparticles, we can confirm the presence of gauche (P H ) and trans (P N ) rotamers in the solid state, the formation of a SS bond in the solution state, the dissociation of the peptide bond and mixing of rotamers because of the SERS effect, and the relative importance of the interaction of sulphyldryl, NH 3 + , and carboxylate groups with the metallic surface. Copyright © 2009 John Wiley & Sons, Ltd.

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DOI: 10.1002/jrs.2175

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