title: Selective detection of 2-nitrobenzenesulfenyl-labeled peptides by matrix-assisted laser desorption/ionization-time of flight mass spectrometry using a novel matrix.
abstract: The 2-nitrobenzenesulfenyl (NBS) method, which is useful for quantitative proteome analysis, is based on stable isotope labeling of tryptophan residues with NBS chloride ((12)C(6)-NBSCl or (13)C(6)-NBSCl). We found that 3-hydroxy-4-nitrobenzoic acid (3H4NBA) is a more suitable matrix than 2,5-dihydroxybenzoic acid (DHB) for detecting NBS-labeled peptides by MALDI-quadrupole IT (QIT)-TOF MS . Furthermore, NBS-labeled peptides were selectively ionized and detected in a mixture of NBS-labeled and unlabeled peptides. Labeled paired peaks were easily detected without enrichment, nonpaired labeled peaks were clearly distinguished from unlabeled contaminating peptides, and nitrotyrosine-containing peptides were also selectively detected on the 3H4NBA matrix, while by-product-peaks arising from nitrobenzene moieties were suppressed. The use of 3H4NBA as a comatrix with CHCA improved the sensitivity of detection while substantially retaining the selectivity of 3H4NBA. The 3H4NBA matrix offers great advantages in terms of simplicity, sensitivity, and usability when used for the NBS method and for MALDI-TOF MS analysis applied to compounds having a nitrobenzene ring.
authors.affiliation: Life Science Laboratory, Shimadzu Corporation, Nakagyo-ku, Kyoto, Japan.
authors.forename: Ei-Ichi
authors.initials: E
authors.lastname: Matsuo
authors.forename: Chikako
authors.initials: C
authors.lastname: Toda
authors.forename: Makoto
authors.initials: M
authors.lastname: Watanabe
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ojima
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Izumi
authors.forename: Koichi
authors.initials: K
authors.lastname: Tanaka
authors.forename: Susumu
authors.initials: S
authors.lastname: Tsunasawa
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishimura
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D009578:Nitrobenzenes; D010455:Peptides / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013194:Staining and Labeling / Q000379:methods*
chemical_list: D009578:Nitrobenzenes; D010455:Peptides; C002732:2-nitrobenzenesulfenyl chloride