title: Selective screening of tyrosine-nitrated peptides in tryptic mixtures by in-source photodissociation at 355 nm in matrix-assisted laser desorption ionization.
abstract: Nitration of tyrosine residues in proteins is an important post-translational modification related to various diseases such as Alzheimer's. In this work, efficient and selective photodissociation (PD) at 355 nm was observed for [M + H](+), [M + H - 16](+), and [M + H - 32](+) generated by matrix-assisted ultraviolet laser desorption ionization (UV-MALDI) of tyrosine-nitrated peptides (nitropeptides). Product ion spectra obtained by post-source PD at this wavelength contained useful information on the amino acid sequence. The spectra for nitropeptides obtained with 355 nm irradiation inside the ion source (MALDI/in-source PD) displayed characteristic triplet patterns due to PD of the above ions. For peptides displaying prominent signal in a MALDI mass map of a tryptic mixture, which are mostly those with arginine at the C-terminus, in-source PD allowed positive identification of their tyrosine-nitrated forms. Identification of such nitropeptides was possible at the 10 fmol level (in tryptic digest of 100 fmol BSA).
authors.affiliation: Department of Chemistry, Seoul National University, Seoul, Korea.
authors.forename: Young Sik
authors.initials: YS
authors.lastname: Shin
authors.forename: Jeong Hee
authors.initials: JH
authors.lastname: Moon
authors.forename: Myung Soo
authors.initials: MS
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D009566:Nitrates / Q000737:chemistry*; D010449:Peptide Mapping; D055668:Photochemical Processes; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014357:Trypsin / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D009566:Nitrates; D014443:Tyrosine; D014357:Trypsin