In relation with the difficulties encountered in previous works concerning the preservation of the S–S linkage in cystine (Cys-Cys dimer) on Ag nanoparticles (NPs), we present here a systematic investigation on both cysteine and cystine as a function of various parameters governing the preparation of metal substrates. Surface-enhanced Raman scattering (SERS) was used as a probe for analyzing (i) the integrity of the disulfide bonds of the adsorbed dimers, (ii) the influence of the metal nature, the reduction protocol as well as the Cys-Cys concentration on the adsorption, (iii) the terminal groups through which the interaction with metal surfaces take place, and (iv) the side chain conformation of the adsorbed molecules. From the whole set of experimental data collected in this work, it appears that large size Au NPs, prepared at low citrate concentration, can be considered as the most appropriate substrates for ensuring the integrity of disulfide linkages. Although Ag NPs prepared with hydroxylamine lead to the cleavage of dimers at low concentration, they have shown their adequacy to keep intact S–S bonds beyond a concentration threshold of ∼200 μM. Based on the examination of the SERS data recorded as a function of dimer concentration, we can now assume that this effect is mainly due to the bidentate and monodentate binding of Cys-Cys dimers at low and high concentrations, respectively, facilitating or not their cleavage on Ag surfaces.

We used surface‐enhanced Raman spectroscopy to investigate the chemical composition of the black stains threatening the rock‐art paintings of Lascaux Cave, Montignac, France. The stains are mainly composed of melanin from the fungus Ochroconis sp. and the faecal pellets of the collembolan Folsomia candida. Surface‐enhanced Raman spectroscopy is a useful technique for revealing the structure of unknown macromolecules in cultural heritage research. Copyright © 2011 John Wiley & Sons, Ltd.

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International audienceDespite numerous investigations devoted to the control of peptide and protein self-assemblies using nanostructured materials, the molecular details of the peptide-material interaction sites remain still under debate. Here, we suggest a solution by using jointly the middle- and low wavenumber regions of surface-enhanced Raman spectra. To achieve our goal, adequately prepared gold and silver colloids, of which the nanofabrication was controlled by means of zeta potential and extinction spectra, were used to enhance the Raman signal arising from a natural fibrillogenic peptide hormone, somatostatin-14, at very low (10–6-to-10–8 M) concentrations. Transmission electron microscopy has revealed that the interacting partners are involved in a mutual aggregation process. In fact, while the presence of plasmonic colloids facilitates the aggregation of the peptide, leading to the formation of the so-called “corona” around nanoparticles, we could observe the appearance of relatively large size peptide-nanoparticle agglomerates in solution. However, the comparison between the data obtained from gold and silver nanoparticles is consistent with the fact that the nature of metal surface, as well as its ionic coverage, considerably affect the peptide binding and subsequent aggregation process. Furthermore, this work led us to conclude that the adsorption of somatostatin-14 on silver nanoparticles is rendered possible through an ionic pair interaction, whereas its anchoring on gold nanoparticles occurs by a direct binding, in which the metal atom and the nitrogen of the unique peptide tryptophan residue are involved

Surface-enhanced Raman spectroscopy (SERS) was used as a powerful surface analyzing tool to investigate the core-shell structural evolution of Au@Pt nanoparticles, revealing the templating role of the underlying Au atoms on the nanoscale Pt-phase structure in the sub-monolayer range.