title: Ultraviolet laser-induced cross-linking in peptides.
abstract: BACKGROUND
  The aim of this study was to demonstrate, and to characterize by high-resolution mass spectrometry that it is possible to preferentially induce covalent cross-links in peptides by using high-energy femtosecond ultraviolet (UV) laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence.
  
  
  METHODS
  Three peptides, xenopsin, angiotensin I, and interleukin, individually or in combination, were exposed to high-energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry.
  
  
  RESULTS
  High-resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters.
  
  
  CONCLUSIONS
  High-energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources.
authors.affiliation: Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di Monte S.Angelo, Napoli, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Leo
authors.forename: Carlo
authors.initials: C
authors.lastname: Altucci
authors.forename: Sandrine
authors.initials: S
authors.lastname: Bourgoin-Voillard
authors.forename: Alfredo M
authors.initials: AM
authors.lastname: Gravagnuolo
authors.forename: Rosario
authors.initials: R
authors.lastname: Esposito
authors.forename: Gennaro
authors.initials: G
authors.lastname: Marino
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Costello
authors.forename: Raffaele
authors.initials: R
authors.lastname: Velotta
authors.forename: Leila
authors.initials: L
authors.lastname: Birolo
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D007834:Lasers; D010455:Peptides / Q000737:chemistry* / Q000528:radiation effects*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods; D014466:Ultraviolet Rays
chemical_list: D000596:Amino Acids; D007477:Ions; D010455:Peptides