title: Interaction of 7-azatryptophan and beta-(1-azulenyl)-alanine with a nitroxyl radical.
abstract: Aal and 7-Atrp, quasi-isosteric with Trp, have been inserted together with a TOAC residue in two 3(10)-helical, model hexapeptides. The interaction of photoexcited AA1 and 7-Atrp with the nitroxide group of TOAC was investigated by time resolved EPR. Both peptides showed nitroxide spin polarized signals revealing that an intramolecular interaction takes places between the excited chromophore and the free radical moiety. The observation of a spin polarized signal in emission for AA1 is accounted for by the formation of triplet azulene by radical promoted enhanced inter system crossing (EISC).
authors.affiliation: Institute of Biomolecular Chemistry, CNR, Department of Organic Chemistry, University of Padova, 35131 Padova, Italy.
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Elena
authors.initials: E
authors.lastname: Sartori
authors.forename: Antonio
authors.initials: A
authors.lastname: Toffoletti
authors.forename: Carlo
authors.initials: C
authors.lastname: Corvaja
authors.forename: Luis
authors.initials: L
authors.lastname: Moroder
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D066298:In Vitro Techniques; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry; D013113:Spin Labels; D014364:Tryptophan / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D005609:Free Radicals; D009589:Nitrogen Oxides; D009842:Oligopeptides; D013113:Spin Labels; C006657:7-azatryptophan; D014364:Tryptophan; C039900:nitroxyl; D000409:Alanine