title: 213 nm Ultraviolet Photodissociation on Peptide Anions: Radical-Directed Fragmentation Patterns.
abstract: Characterization of acidic peptides and proteins is greatly hindered due to lack of suitable analytical techniques. Here we present the implementation of 213 nm ultraviolet photodissociation (UVPD) in high-resolution quadrupole-Orbitrap mass spectrometer in negative polarity for peptide anions. Radical-driven backbone fragmentation provides 22 distinctive fragment ion types, achieving the complete sequence coverage for all reported peptides. Hydrogen-deficient radical anion not only promotes the cleavage of Cα-C bond but also stimulates the breaking of N-Cα and C-N bonds. Radical-directed loss of small molecules and specific side chain of amino acids are detected in these experiments. Radical containing side chain of amino acids (Tyr, Ser, Thr, and Asp) may possibly support the N-Cα backbone fragmentation. Proline comprising peptides exhibit the unusual fragment ions similar to reported earlier. Interestingly, basic amino acids such as Arg and Lys also stimulated the formation of abundant b and y ions of the related peptide anions. Loss of hydrogen atom from the charge-reduced radical anion and fragment ions are rationalized by time-dependent density functional theory (TDDFT) calculation, locating the potential energy surface (PES) of ππ* and repulsive πσ* excited states of a model amide system.
authors.affiliation: Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Halim
authors.affiliation: Institut des Sciences Analytiques, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Girod
authors.affiliation: Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
authors.forename: Luke
authors.initials: L
authors.lastname: MacAleese
authors.affiliation: Institut des Sciences Analytiques, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lemoine
authors.affiliation: Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France.
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Antoine
authors.affiliation: Institut Lumière Matière, Université Lyon 1 - CNRS, Université de Lyon, 69622, Villeurbanne Cedex, France. phillipe.dugourd@univ-lyon1.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Dugourd
mesh_terms: D000595:Amino Acid Sequence; D007477:Ions / Q000737:chemistry; D013058:Mass Spectrometry; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D010782:Photolysis; D014466:Ultraviolet Rays
chemical_list: D007477:Ions; D010455:Peptides
keywords: Peptide; Photo-fragmentation; Radical anions; TDDFT; UVPD