title: Characterization of reaction products formed in a model reaction between pentanal and lysine-containing oligopeptides.
abstract: Aldehydes formed as a result of lipid oxidation form fluorophores after binding to proteins. The structure of the fluorophores formed by reaction between saturated aldehydes and lysine has not yet been identified. The reaction products formed in the reaction between pentanal and oligopeptides were studied by fluorescence spectroscopy and mass spectrometry. The emission spectra showed an increase in fluorescence intensity with incubation time, and the rates were linear with the concentration of pentanal. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses of the reaction products suggested a molar relation for peptide:pentanal of 1:4. Further tandem mass spectrometry analysis of one of the modified peptides (Pro-Thr-His-Ile-Lys-Trp-Gly-Asp) strongly suggested binding of one pentanal molecule to the amino terminal proline and three pentanal molecules bound to the lysine residue. The latter species is suggested to be the actual fluorophore, through the formation of conjugated double bonds, and a possible reaction pathway through a combination of aldol condensation of pentanal and Schiff base formation with the lysine is suggested.
authors.affiliation: Danish Institute of Agricultural Sciences, Department of Food Science, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark.
authors.forename: Trine K
authors.initials: TK
authors.lastname: Dalsgaard
authors.forename: Jacob H
authors.initials: JH
authors.lastname: Nielsen
authors.forename: Lotte B
authors.initials: LB
authors.lastname: Larsen
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000595:Amino Acid Sequence; D008239:Lysine / Q000032:analysis* / Q000737:chemistry; D013058:Mass Spectrometry; D009842:Oligopeptides / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000447:Aldehydes; D009842:Oligopeptides; C046012:pentanal; D008239:Lysine