TANDEM QUADRUPOLE MASS SPECTROMETRY OF SULFATIDES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Sulfatides yield intense deprotonated molecular species ([M - H]-) in negative-ion mode by electrospray ionization. The product-ion spectra of the [M - H]- ions of sulfatides obtained with a tandem quadrupole and with an ion-trap mass spectrometers contain abundant fragment ions informative for structural determination of the long-chain base and the fatty acid constituent including the location of its unsaturated bond. Identifications of sulfatides in mixtures, or specific sulfatide subclasses that are varied by long-chain base, or differentiation of sulfatide class with a-hydroxy fatty acid substituent from that with non-hydroxy fatty acid group can be facilitated by precursor ion or constant neutral loss scans. While CAD product-ion spectra of the [M - H]- ions are useful for differentiation of isomeric structures, the mechanisms underlying the fragmentation processes for sulfatides under low-energy CAD can be unveiled by multiple-stage ion-trap tandem mass spectrometry of various sulfatides, including their H-D exchanged analogs. The sensitivity of sulfatides observed as the [M + Na]+ ions by ESI in the positive-ion mode, on the other hand, is poor. The product-ion spectra of the [M + Na]+ ions of sulfatides contain very few structurally informative ions and are not useful for structural identification.