Selective Screening of Tyrosine-Nitrated Peptides in Tryptic Mixtures by In-Source Photodissociation at 355 nm in Matrix-Assisted Laser Desorption Ionization

• Published in: Analytical chemistry (Washington) 2011-03, Vol.83 (5), p.1704-1708
• Main Authors: Shin, Young Sik, Moon, Jeong Hee, Kim, Myung Soo
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Analytical chemistry; Chemistry; Desorption; Exact sciences and technology; Ions; Nitrates; Nitrates - chemistry; Peptide Mapping; Peptides; Photochemical Processes; Spectrometric and optical methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Trypsin - chemistry; Tyrosine - chemistry; Ultraviolet Rays
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac1028352

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).