title: Photodetachment of tryptophan anion: an optical probe of remote  electron.
abstract: The UV photoexcitation spectrum of deprotonated tryptophan anion is presented. Singly deprotonated amino-acid tryptophan has been produced in an electrospray ionization source, isolated in a quadrupole ion trap and photoexcited with a UV tunable laser, resulting in the photodetachment of the excess electron. Whereas no influence of the proton on the UV spectrum of tryptophan was previously reported (Phys. Chem. Chem. Phys., 2004, 6, 2633; J. Chem. Phys., 2005, 122, 074310), we observe a strong bathochromism due to the presence of the negatively charged group in the vicinity of the chromophore. An excellent agreement with TD-DFT (time dependent density functional theory) predictions for the absorption spectrum of the lowest energy conformer is found. The sensitivity of the tryptophan chromophore to the presence of a remote negative charge offers new perspectives for charge mapping in large biomolecules.
authors.affiliation: Université de Lyon, Université Lyon 1, CNRS, UMR5579, LASIM, 69622 Villeurbanne, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Compagnon
authors.forename: Abdul-Rahman
authors.initials: AR
authors.lastname: Allouche
authors.forename: Franck
authors.initials: F
authors.lastname: Bertorelle
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Antoine
authors.forename: Philippe
authors.initials: P
authors.lastname: Dugourd
mesh_terms: D000838:Anions; D004583:Electrons; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D000838:Anions; D014364:Tryptophan