|Organization or Institution||University of Florida|
Fatty acid isomer quantification in mouse brain tissues using gas-phase charge inversion ion/ion reactions enabled on an FTICR mass spectrometer
Julia R. Bonney; Boone M. Prentice
University of Florida, Gainesville, FL
Fatty acids play important biological roles in many disease pathways, and accurate structural characterization of these metabolites in imaging mass spectrometry (IMS) analyses is critical to understanding their biochemical functions. While fatty acids can be detected with high sensitivity using IMS, very little structural information is provided upon traditional tandem mass spectrometry (MS/MS). Conducting a derivatization in the gas phase using ion/ion reactions affords the ability to rapidly transform the fatty acid analyte to a more structurally informative ion type without manipulating the original tissue sample. Herein, gas-phase charge inversion ion/ion reactions were performed on a 7T FTICR MS (Bruker Daltonics). Briefly, fatty acid anions generated by matrix-assisted laser desorption/ionization (MALDI) and doubly charged tris-phenanthroline magnesium metal cation complexes, [Mg(Phen)3]2+, generated by electrospray ionization (ESI) were alternatively isolated using a quadrupole mass filter and injected into a hexapole reaction cell. Following a mutual storage ion/ion reaction period (~1400 ms), the resulting fatty acid/metal complex is transferred to the ICR cell where it is subjected to sustained off-resonance collision induced dissociation (SORI CID) and then mass analyzed. This methodology has been used to identify the double bond position in fatty acid isomers oleic acid (18:1 Δ9) and cis-vaccenic acid (18:1 Δ11) and to construct calibration curves that enable the quantification of fatty acid double bond positional isomer ratios from mouse brain tissue.