title: Photoinduced electron transfer through peptide-based self-assembled monolayers chemisorbed on gold electrodes: directing the flow-in and flow-out of electrons through peptide helices.
abstract: Photoinduced electron transfer (PET) experiments have been carried out on peptide self-assembled monolayers (SAM) chemisorbed on a gold substrate. The oligopeptide building block was exclusively formed by C(α)-tetrasubstituted α-aminoisobutyric residues to attain a helical conformation despite the shortness of the peptide chain. Furthermore, it was functionalized at the C-terminus by a pyrene choromophore to enhance the UV photon capture cross-section of the compound and by a lipoic group at the N-terminus for linking to gold substrates. Electron transfer across the peptide SAM has been studied by photocurrent generation experiments in an electrochemical cell employing a gold substrate modified by chemisorption of a peptide SAM as a working electrode and by steady-state and time-resolved fluorescence experiments in solution and on a gold-coated glass. The results show that the electronic flow through the peptide bridge is strongly asymmetric; i.e., PET from the C-terminus to gold is highly favored with respect to PET in the opposite direction. This effect arises from the polarity of the Au-S linkage (Au(δ+)-S(δ-), junction effect) and from the electrostatic field generated by the peptide helix.
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome "Tor Vergata" , 00133 Rome, Italy.
authors.forename: Mariano
authors.initials: M
authors.lastname: Venanzi
authors.forename: Emanuela
authors.initials: E
authors.lastname: Gatto
authors.forename: Mario
authors.initials: M
authors.lastname: Caruso
authors.forename: Alessandro
authors.initials: A
authors.lastname: Porchetta
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D055664:Electrochemical Techniques; D004566:Electrodes; D004579:Electron Transport; D004583:Electrons; D006046:Gold / Q000737:chemistry*; D008968:Molecular Conformation; D010455:Peptides / Q000737:chemistry*; D055668:Photochemical Processes; D013050:Spectrometry, Fluorescence
chemical_list: D010455:Peptides; D006046:Gold