Long-range electron transfer in rigid 3(10)-helical oligopeptides containing redox cyclic alpha-amino acids.
Intrahelical photoinduced electron transfer processes (ET) in conformationally restricted oligopeptides have been studied by nanosecond time-resolved transient spectroscopy. The helical peptides were constructed from sterically hindered alpha-aminoisobutyric acid (Aib) and two cyclic alpha-amino acids (Aib class) bearing electron acceptor and donor side chains (DkNap, ThQx). This helical backbone design provides high conformation stability, as previously demonstrated, and yields reliable 3(10)-helical architectures in solution. The forward ET between ThQx and 3DkNap is followed by a slow back ET thus giving rise to an accumulation of the charge-separated ion pairs for hundreds of nanoseconds. We demonstrate the modulation of electronic interactions by the number of intervening Aib residues separating acceptor-donor side chains and propose modifications of the peptide framework by inclusion of a non-Aib amino acid residue. These well-defined and sterically stable frameworks are suited for the precise evaluation of intrahelical electron transfer processes mediated by peptides.
Lang
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Department of Chemistry, University of California, Santa Cruz, USA. lang@iic.cas.cz
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D000621:Aminoisobutyric Acids / Q000737:chemistry; D004579:Electron Transport; D066298:In Vitro Techniques; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D017433:Protein Structure, Secondary
D000621:Aminoisobutyric Acids; D009842:Oligopeptides; C100049:2-aminoisobutyric acid