title: Identification of selenium-containing glutathione S-conjugates in a yeast extract by two-dimensional liquid chromatography with inductively coupled plasma MS and nanoelectrospray MS/MS detection.
abstract: An approach for the identification of unknown selenium-containing biomolecules was developed, enabling the identification of selenodiglutathione (GS-Se-SG) and the mixed selenotrisulfide of glutathione and cysteinylglycine (GS-Se-SCG) in aqueous yeast extracts. The method consists of two-dimensional liquid chromatography, inductively coupled plasma mass spectrometry (ICPMS) and nanoelectrospray tandem mass spectrometry. Analytes were separated by size-exclusion chromatography followed by preconcentration and separation on a porous graphitic carbon HPLC column. The HPLC effluent was monitored for selenium by ICPMS, and two selenium-containing fractions were isolated and analyzed by nanoelectrospray MS. The nanoelectrospray technique has a low sample consumption of approximately 80 nL/min, enabling a preconcentration of the sample to a few microliters. Mass spectra of the two fractions showed the characteristic Se isotopic pattern centered at m/z 693.1 and 564.0 for the [M + H]+ 80Se ions. MS/MS spectra of adjacent parent ions confirmed the presence of Se. The two selenium species were identified as GS-Se-SG and GS-Se-SCG by collision induced dissociation (CID). The accurately measured masses of the most abundant 691 and 693 u parent ions are in good agreement (differences = 3 ppm) with the theoretical masses. To our knowledge, this is the first identification of GS-Se-SG and GS-Se-SCG in biological matrixes by MS/MS.
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004151:Dipeptides / Q000737:chemistry*; D005978:Glutathione / Q000031:analogs & derivatives* / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D016566:Organoselenium Compounds / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D012643:Selenium / Q000032:analysis*; D018036:Selenium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*
chemical_list: D004151:Dipeptides; D016566:Organoselenium Compounds; D018036:Selenium Compounds; D013440:Sulfides; C059755:selenotrisulfide; C017710:selenodiglutathione; C028505:cysteinylglycine; D005978:Glutathione; D012643:Selenium