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Unusual negative charge‐directed fragmentation: collision‐induced dissociation of cyclopentenone oxylipins in negative ion mode
Author(s) -
Bao Jiangyin,
Gao Xiaoli,
Jones A. Daniel
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6803
Subject(s) - cyclopentenone , chemistry , oxylipin , fragmentation (computing) , deprotonation , electrophile , dissociation (chemistry) , stereochemistry , organic chemistry , ion , enzyme , computer science , catalysis , operating system
RATIONALE Oxidized fatty acids, and particularly cyclopentenone oxylipins, are electrophilic metabolites that play diverse physiological roles. Current understanding is limited regarding how ion fragmentation provides essential information about oxylipin structures. In this work, unusual products of the collisional activation of deprotonated cyclopentenone oxylipins were investigated. METHODS The cyclopentenone oxylipin 12‐oxo‐phytodienoic acid (OPDA) and its 18 O‐labeled forms were ionized using negative‐ion mode electrospray ionization, and product ion tandem mass (MS/MS) spectra were generated using collision‐induced dissociation (CID). CID‐MS/MS spectra were also generated for several cyclopentenone prostaglandins. RESULTS Upon collisional activation, deprotonated cyclopentenone oxylipins 12‐oxo‐phytodienoic acid (OPDA) and dinorOPDA form a characteristic and dominant product ion at m/z 165 that is attributed to charge‐directed hydride migration to the electrophilic enone ring followed by elimination of neutral C 7 H 10 O 2 from the carboxyl end. In contrast, pseudo‐MS 3 spectra of deprotonated cyclopentenone prostaglandins exhibited a different fragmentation behavior, in that cleavage near C = C bonds is directed by the carbonyl group in the nearby cyclopentenone ring. CONCLUSIONS Two different routes of fragmentation are proposed for cyclopentenone fatty acids with saturated and unsaturated side chains. We predict that this behavior may facilitate the identification of novel cyclopentenone oxylipins and accelerate discoveries of their biological regulatory functions. Copyright © 2014 John Wiley & Sons, Ltd.