title: Gold nanoclusters protected by conformationally constrained peptides.
abstract: The preparation and properties of a series of gold nanoclusters protected by thiolated peptides based on the alpha-aminoisobutyric acid (Aib) unit are described. The peptides were devised to form 0-3 C=O...H-N intramolecular hydrogen bonds, as required by their 3(10)-helical structure. The monolayer-protected clusters (MPCs) were prepared, using a modified version of the two-phase Brust-Schiffrin preparation, and fully characterized with (1)H NMR spectrometry, IR and UV-vis absorption spectroscopies, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The MPCs were obtained with core diameters in the range of 1.1-2.3 nm, depending on the reaction conditions. Structured peptides formed smaller clusters. The smallest MPC obtained is in agreement with the average formula Au(38)Pep(18). The results showed that the chemical integrity of the peptide is maintained upon monolayer formation and that the average number of peptide ligands per gold cluster is typically 75-85% the value calculated for alkanethiolate MPCs of similar sizes. The IR and NMR spectra indicated that in the monolayer the peptides are involved in both intra- and interligand C=O...H-N hydrogen bonds.
authors.affiliation: Department of Chemistry, University of Padua, via Marzolo 1, 35131 Padua, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Fabris
authors.forename: Sabrina
authors.initials: S
authors.lastname: Antonello
authors.forename: Lidia
authors.initials: L
authors.lastname: Armelao
authors.forename: Robert L
authors.initials: RL
authors.lastname: Donkers
authors.forename: Federico
authors.initials: F
authors.lastname: Polo
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
authors.forename: Flavio
authors.initials: F
authors.lastname: Maran
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D008024:Ligands; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013818:Thermogravimetry
chemical_list: D000621:Aminoisobutyric Acids; D008024:Ligands; D010455:Peptides; C100049:2-aminoisobutyric acid; D006046:Gold