TANDEM QUADRUPOLE MASS SPECTROMETRY OF SPHINGOMYELIN

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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. Low-energy collisionally activated dissociation (CAD) tandem quadrupole and multiple-stage ion-trap (IT) mass spectrometry with electrospray ionization provide sensitive methods for complete structural characterization of sphingomyelin. Sphingomyelin readily forms abundant [M + Cat]+ ions (where Cat = Li, Na, or K) in the presence of alkali metal ion, when being subjected to electrospray ionization (ESI). Following low-energy CAD, the [M + Li]+ ions of sphingomyelin yield abundant fragment ions that identify both the fatty acyl constituent and the long-chain base of the molecule. Tandem quadrupole mass spectrometry with precursor ion or constant neutral loss scans facilitates identification of specific sphingomyelin subclasses that are varied by the long-chain base, or by the fatty acid substituents. The multiple-stage IT mass spectrometry, on the other hand, provides a powerful tool to get insight into the mechanisms underlying the fragmentation processes, and to perform structural characterization using the MS5-spectra for sphingomyelins. The applications of tandem quadrupole and multiple-stage IT mass spectrometry for differentiation among sphingomyelin isomers are also presented.