Rapid differentiation of isomeric lipids by photodissociation mass spectrometry of fatty acid derivatives

Pham, H. T., Trevitt, A. J., Mitchell, T. W., & Blanksby, S. J. (2013) Rapid differentiation of isomeric lipids by photodissociation mass spectrometry of fatty acid derivatives. Rapid Communications in Mass Spectrometry, 27(7), pp. 805-815.

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RATIONALE Both traditional electron ionization and electrospray ionization tandem mass spectrometry have demonstrated limitations in the unambiguous identification of fatty acids. In the former case, high electron energies lead to extensive dissociation of the radical cations from which little specific structural information can be obtained. In the latter, conventional collision-induced dissociation (CID) of even-electron ions provides little intra-chain fragmentation and thus few structural diagnostics. New approaches that harness the desirable features of both methods, namely radical-driven dissociation with discrete energy deposition, are thus required. METHODS Herein we describe the derivatization of a structurally diverse suite of fatty acids as 4-iodobenzyl esters (FAIBE). Electrospray ionization of these derivatives in the presence of sodium acetate yields abundant [M+Na]+ ions that can be mass-selected and subjected to laser irradiation (=266nm) on a modified linear ion-trap mass spectrometer. RESULTS Photodissociation (PD) of the FAIBE derivatives yields abundant radical cations by loss of atomic iodine and in several cases selective dissociation of activated carboncarbon bonds (e.g., at allylic positions) are also observed. Subsequent CID of the [M+NaI]center dot+ radical cations yields radical-directed dissociation (RDD) mass spectra that reveal extensive carboncarbon bond dissociation without scrambling of molecular information. CONCLUSIONS Both PD and RDD spectra obtained from derivatized fatty acids provide a wealth of structural information including the position(s) of unsaturation, chain-branching and hydroxylation. The structural information obtained by this approach, in particular the ability to rapidly differentiate isomeric lipids, represents a useful addition to the lipidomics tool box. Copyright (c) 2013 John Wiley & Sons, Ltd.

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22 citations in Scopus
23 citations in Web of Science®
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ID Code: 68929
Item Type: Journal Article
Refereed: Yes
Additional URLs:
Keywords: double-bond position, radical-directed dissociation, ozone-induced, dissociation, electrospray-ionization, methyl-esters, structural-analysis, unsaturated lipids, picolinyl esters, gas-phase, identification
DOI: 10.1002/rcm.6503
ISSN: 0951-4198
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Wiley-Blackwell
Deposited On: 20 Mar 2014 03:46
Last Modified: 20 Feb 2015 02:53

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