title: Enhanced detection of sulfo-peptides as onium salts in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
abstract: A new two-component system, consisting of a matrix and an onium salt as comatrix, is described for detection of sulfo-peptides in the positive mode by matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Binary iodonium salts were superior to quaternary phosphonium salts in terms of suppression of desulfation and salt formation with the carboxyl group. Of the iodonium salts examined, bis(4-tert-butylphenyl)iodonium (BTI) hexafluorophosphate and bromide were most effective in giving intensive molecular ion signals in the form of [M(BTI)+BTI](+). The conditions optimized for O-sulfated tyrosine-containing peptides could be applicable for O-sulfated serine- and threonine-containing peptides. In the case of a phospho-peptide, a molecular ion appeared more intensively as a proton adduct than as a BTI adduct.
authors.affiliation: Department of Applied Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. maueki@rs.kagu.tus.ac.jp
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ueki
authors.forename: Miyuki
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D002766:Cholecystokinin / Q000032:analysis; D007202:Indicators and Reagents; D009842:Oligopeptides / Q000032:analysis; D009861:Onium Compounds / Q000032:analysis*; D010455:Peptides / Q000032:analysis*; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013457:Sulfur Compounds / Q000032:analysis*
chemical_list: D007202:Indicators and Reagents; D009842:Oligopeptides; D009861:Onium Compounds; D010455:Peptides; D013457:Sulfur Compounds; D002766:Cholecystokinin