Ozone-induced dissociation of conjugated lipids reveals significant reaction rate enhancements and characteristic odd-electron product ions

Pham, H. T., Maccarone, A. T., Campbell, J. L., Mitchell, T. W., & Blanksby, Stephen J. (2013) Ozone-induced dissociation of conjugated lipids reveals significant reaction rate enhancements and characteristic odd-electron product ions. Journal of the American Society for Mass Spectrometry, 24(2), pp. 286-296.

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Abstract

Ozone-induced dissociation (OzID) is an alternative ion activation method that relies on the gas phase ion-molecule reaction between a mass-selected target ion and ozone in an ion trap mass spectrometer. Herein, we evaluated the performance of OzID for both the structural elucidation and selective detection of conjugated carbon-carbon double bond motifs within lipids. The relative reactivity trends for [M + X](+) ions (where X = Li, Na, K) formed via electrospray ionization (ESI) of conjugated versus nonconjugated fatty acid methyl esters (FAMEs) were examined using two different OzID-enabled linear ion-trap mass spectrometers. Compared with nonconjugated analogues, FAMEs derived from conjugated linoleic acids were found to react up to 200 times faster and to yield characteristic radical cations. The significantly enhanced reactivity of conjugated isomers means that OzID product ions can be observed without invoking a reaction delay in the experimental sequence (i.e., trapping of ions in the presence of ozone is not required). This possibility has been exploited to undertake neutral-loss scans on a triple quadrupole mass spectrometer targeting characteristic OzID transitions. Such analyses reveal the presence of conjugated double bonds in lipids extracted from selected foodstuffs. Finally, by benchmarking of the absolute ozone concentration inside the ion trap, second order rate constants for the gas phase reactions between unsaturated organic ions and ozone were obtained. These results demonstrate a significant influence of the adducting metal on reaction rate constants in the fashion Li > Na > K.

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ID Code: 68927
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: Ozone-induced dissociation, Conjugated linoleic acid, Ion-molecule, reactions, Lipidomics, Rate constants, Mass spectrometry, linoleic-acid isomers, tandem mass-spectrometry, double-bond position, body-composition, methyl-esters, fatty-acids, gas-phase, mice, identification, ionization
DOI: 10.1007/s13361-012-0521-9
ISSN: 1879-1123 (online) 1044-0305 (print)
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Funding:
Copyright Owner: Copyright 2013 American Society for Mass Spectrometry, Springer
Deposited On: 20 Mar 2014 03:41
Last Modified: 29 Jan 2016 02:33

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