title: Anomalous distance dependence of electron transfer across peptide bridges.
abstract: The first investigation on the distance dependence of a dissociative electron transfer process across peptide bridges is reported. This study was carried out by using a series of donor-peptide-acceptor systems in which the donor is a phthalimido moiety, the peptide bridges are provided by alpha-aminoisobutyric acid (Aib) homooligomers, and the acceptor is a peroxide functional group. The intramolecular electron transfer from the electrogenerated phthalimido radical anion to the peroxide was studied in comparison with the thermodynamic and kinetic information obtained with models of the acceptor and the donor. The intramolecular rate constants were determined in N,N-dimethylformamide by taking into account the corresponding intermolecular values. The experimental results point to an unusual non-exponential dependence of the intramolecular electron transfer rate on the number of bridge units. The same trend could be verified also by taking into account the actual donor-acceptor edge-to-edge distance. The peculiar distance dependence that was observed for the intramolecular electron transfer rate is attributed to the mediating effect of the intramolecular C=O...H-N hydrogen bonds.
authors.affiliation: Dipartimento di Chimica Fisica, Università di Padova, via Loredan 2, 35131 Padova, Italy.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Antonello
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moretto
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*; D004563:Electrochemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D000621:Aminoisobutyric Acids; D010455:Peptides; C100049:2-aminoisobutyric acid