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Liquid chromatography/tandem mass spectrometric analysis of 7,10‐dihydroxyoctadecenoic acid, its isotopomers, and other 7,10‐dihydroxy fatty acids formed by Pseudomonas aeruginosa 42A2
Author(s) -
Nilsson Tomas,
Martínez Eriel,
Manresa Angeles,
Oliw Ernst H.
Publication year - 2010
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.4446
Subject(s) - chemistry , isotopomers , chromatography , tandem , pseudomonas aeruginosa , organic chemistry , bacteria , molecule , materials science , biology , composite material , genetics
Pseudomonas aeruginosa is an opportunistic pathogen, which oxidizes oleic acid to 7( S ),10( S )‐dihydroxy‐8( E )‐octadecenoic acid (7,10‐(OH) 2 ‐18:1) of biological and industrial interest. Electrospray tandem mass spectrometric (MS/MS) analysis of hydroxylated fatty acids usually generates characteristic fragments containing the carboxylate anion and formed by α ‐cleavage at the oxidized carbon. These fragments indicate the positions of the hydroxyl group. In contrast, liquid chromatography (LC)/MS/MS analysis of 7,10‐(OH) 2 ‐18:1 yielded a series of other ions with structural information. To study the fragmentation mechanism, we prepared 2 H‐ and 18 O‐labeled isotopomers. We also performed MS 3 analysis of the major ions, and for comparison we generated the corresponding 7,10‐dihydroxy metabolites of 16:1n‐7, 18:2n‐6, and 20:1n‐11 with a protein extract of P . aeruginosa . The MS/MS spectra of 7,10‐(OH) 2 ‐18:1 and its isotopomers, 7,10‐(OH) 2 ‐16:1, and 7,10‐(OH) 2 ‐20:1, contained a series of prominent fragments that all hold the omega end. The 8,9‐double bond was not essential for this fragmentation, as 7,10‐(OH) 2 ‐18:0, and its isotopomers, formed essentially the same fragments in the lower mass range. In contrast, 7,10‐dihydroxy‐8( E ),12( Z )‐octadecadienoic acid (7,10‐(OH) 2 ‐18:2) fragmented by α ‐cleavage at the oxidized carbons with formation of carboxylate anions. Our results demonstrate that C 16 –C 20 fatty acids with a 7,10‐dihydroxy‐8( E ) functionality undergo charge‐driven fragmentation after charge migration to the ω ‐end, whereas the main ions of 7,10‐(HO) 2 ‐18:2 retain charge at the carboxyl group. Copyright © 2010 John Wiley & Sons, Ltd.