title: Fragmentation characteristics of peptide-metal ion adducts under matrix-assisted laser desorption/ionization post-source decay time-of-flight mass spectrometric conditions.
abstract: Fragmentation reactions of sodium-cationized enkephalin peptides generated by matrix-assisted laser desorption/ionization were studied using post-source decay (PSD) with a reflectron time-of-flight mass spectrometer. Several matrices and analyte-matrix sample preparation methods were evaluated for high-intensity ion currents that could last for the entire PSD analysis. A triple dried-droplet sample preparation procedure with 2,5-dihydroxybenzoic acid as the matrix was found to yield abundant longer-lasting ion signals of the peptide-Na(+) ion adducts. The principal decay product of these adduct ions is the [b(n-1) + Na + OH](+) ion, which provides an unambiguous identification of the C-terminal residue of a peptide. In some peptides, the loss of a second residue from the C-terminus is also observed. No other sequence-specific ions were observed.
authors.affiliation: Department of Chemistry, University of Memphis, Memphis, Tennessee 38152, USA.
authors.forename: Dhammika
authors.initials: D
authors.lastname: Jayawardene
authors.forename: Chhabil
authors.initials: C
authors.lastname: Dass
mesh_terms: D000595:Amino Acid Sequence; D004745:Enkephalins / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis*; D017421:Sequence Analysis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D004745:Enkephalins; D007477:Ions; D010455:Peptides