title: 18O-labeling quantitative proteomics using an ion trap mass spectrometer.
abstract: We describe a method for simultaneous identification and quantitation of proteins within complex mixtures. The method consists of 18O-labeling, a simple stable isotope-coding that requires merely enzymatic digestion in 18O-water, in combination with a capillary-liquid chromatography electrospray ion-trap mass spectrometer. In a separate experiment using the same sample and a spike test, we demonstrate that the difference ration was calculated accurately using the 18O-labeling method even if the protein was part of a complex mixture. Our data also suggest that the accuracy of the quantitation can be improved by averaging the difference ratios of several peptides. In comparing our method with the isotope-coded affinity tag (ICAT) method, we show that the 18O-labeling method has the advantages of better recovery and fewer isotope effects. Therefore, the 18O-labeling method is a powerful tool for large-scale proteomics applications.
authors.affiliation: Genomic Science Laboratories, Sumitomo Pharmaceuticals Co., Ltd., Osaka 554-0022, Japan. sakai@sumitomopharm.co.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Sakai
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kojima
authors.forename: Kazunori
authors.initials: K
authors.lastname: Yanagi
authors.forename: Masaharu
authors.initials: M
authors.lastname: Kanaoka
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D010103:Oxygen Isotopes / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D040901:Proteomics; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D010103:Oxygen Isotopes; D010455:Peptides; D011506:Proteins