Negative electrospray ionization low‐energy tandem mass spectrometry of hydroxylated fatty acids: a mechanistic study

Moe, Morten K.; Strøm, Morten B.; Jensen, Einar; Claeys, Magda

doi:10.1002/rcm.1545

Cited by 48 publications

(69 citation statements)

References 26 publications

(37 reference statements)

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“…cated similar hydrogen migrations to account for fragments in the resonance electron capture mass spectra of deuterated palmitic acid. Hydrogen migrations from hydroxy-groups to the carboxy function of hydroxy fatty acid anions have recently been observed by Moe et alé [57]ébutéinénoneéofétheélatteréthreeéreportsé [55][56][57], however, was the charge proposed to migrate to the aliphatic chain as proposed here.…”

Section: Negative Ions Of the [M ϫ C N H 2nϩ2 ]mentioning

confidence: 54%

A new charge-associated mechanism to account for the production of fragment ions in the high-energy CID spectra of fatty acids

Harvey¹

2005

J. Am. Soc. Mass Spectrom.

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A new mechanism, termed a charge-assisted process, is proposed as an additional mechanism to the charge-remote process to account for ions of the [M Ϫ C n H 2nϩ2 ] series found in the positive and negative high energy CID spectra of fatty acids and related compounds when ionized as closed-shell ( [M Ϫ H] Ϫ or [M ϩ X] ϩ ) species. The new mechanism is based on that commonly invoked to account for similar ions in the electron-impact spectra of derivatized fatty acids whereby the positive charge on the derivative abstracts a hydrogen atom from various positions of the alkyl chain to leave a radical that initiates a radical-induced cleavage of the chain. It is proposed that in the high energy CID spectra of closed-shell ions, similar hydrogen migrations occur but unpairing of electrons is avoided by charge transfer to the alkyl chain. This charge then initiates a concerted cleavage of the chain to give an allylic carbonium (positive ion spectrum) or carbanion (negative ion spectrum). The mechanism avoids the need to involve radicals or loss of hydrogen atoms from even-electron (closed shell) ions and provides a driving force for the reaction, namely, the formation of ions with a stabilized charge. An extension of the mechanism is also proposed to account for the formation of odd-electron ions from these compounds. The charge-assisted mechanism does not rule out the occurrence of other mechanisms that have been accepted for many years but provides an alternative process that can account for some spectral features which were difficult to explain earlier. show remarkable similarities with those of their oddelectron counterparts produced by EI [18,22,23,28,42]. The major fragment ions in these high energy CID spectra are even-electron (closed shell) species belonging to the [M Ϫ C n H 2nϩ2 ] series but also present, depending on the ionization conditions and internal energy of the ions, are other series, predominantly of the composition [M Ϫ C n H 2nϩ1 ] [41] that have odd numbers of electrons and must be radicals. Hydrogen atom loss has frequently been proposed to account, not only for this ion series, but to be involved in the formation of the major, closed-shell C n H 2nϩ2 ion series [23,28] even though such a mechanism involves the energetically unfavorable unpairing of electrons. Much of the fragmentation of the high energy, evenelectron CID ions has been rationalized by charge-remote mechanisms of the type first proposed by Gross and co-workers in the 1980s [33,[43][44][45]. Thus, Jensen et al.

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Section: Negative Ions Of the [M ϫ C N H 2nϩ2 ]mentioning

confidence: 54%

A new charge-associated mechanism to account for the production of fragment ions in the high-energy CID spectra of fatty acids

Harvey¹

2005

J. Am. Soc. Mass Spectrom.

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“…15 We found that 7,10-(OH) 2 -18:1 yielded a complex MS/MS spectrum, which did not harmonize with the predictable and reported fragmentation pattern of other dihydroxy fatty acids. 10,[12][13][14] This was in contrast to its GC/MS spectrum. 4 The first goal of our study was to perform a systematic investigation of the MS/MS fragmentation mechanism of 7,10-(OH) 2 -18:1 and related dihydroxy fatty acids.…”

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confidence: 81%

Liquid chromatography/tandem mass spectrometric analysis of 7,10-dihydroxyoctadecenoic acid, its isotopomers, and other 7,10-dihydroxy fatty acids formed byPseudomonas aeruginosa42A2

Nilsson

Martínez

Manresa

et al. 2010

Rapid Commun. Mass Spectrom.

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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 alpha-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 alpha-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 omega-end, whereas the main ions of 7,10-(HO)(2)-18:2 retain charge at the carboxyl group.

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“…This suggests that the ion is formed by more than one mechanism. Scheme 2 displays three charge-directed mechanisms proposed to operate in 9,10,12,13-(OH) 4 -18:0 derived from our previous work [35]. Mechanism 2b shows that the ion at m/z 201 also is formed by this mechanism.…”

Section: :0/9101213-(oh) 4 -18:0 Psmentioning

confidence: 97%

“…In addition, ions determining the position of the two hydroxyl groups are observed. These ions are results of COC cleavages adjacent to the hydroxyl groups, as outlined in Scheme 1 (lower part) [35]. The ions at m/z 229 and 199 are presumably formed by homolytic cleavage of the C13OC12 and the C12OC11 bond with subsequent loss of a hydrogen radical (Scheme 1a and 1b, respectively), with the charge retained at the carboxylate group.…”

Section: Structure Characterization Of Pls In Generalmentioning

confidence: 98%

Total structure characterization of unsaturated acidic phospholipids provided by vicinal di-hydroxylation of fatty acid double bonds and negative electrospray ionization mass spectrometry

Moe

Anderssen

Strøm

et al. 2005

J. Am. Soc. Mass Spectrom.

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In the present work, the unsaturated fatty acid substituents of some phosphatidic acid, phosphatidylserine, phosphatidylinositol, and phosphatidylglycerol species were converted to their 1,2-di-hydroxy derivatives by OsO 4 . The subsequent electrospray ionization tandem low-energy mass spectrometry analysis of the deprotonated species allowed positional determination of the double bonds by the production of specific product-ions. The productions are formed by charge-remote and charge-proximate homolytic cleavages as well as charge-directed heterolytic cleavages and rearrangements. The commercial availability of pure species of the phospholipids in question was limited, and a number of species were therefore synthesized. The developed method was used to fully characterize the two isobaric phosphatidylglycerol species 16:0/16:1⌬ 9 and 16:0/16:1⌬ 10 extracted from the bacteria Methylococcus capsulatus. The presence of these fatty acids was supported by a gas-chromatography mass spectrometry investigation of the dimethyloxazoline derivatives of the species of the lipid extract. The present work demonstrates that a total structure characterization of acidic unsaturated phospholipids in isolate or in mixtures is accomplished by vicinal di-hydroxylation of olefinic sites and subsequent electrospray ionization mass spectrometry of the derivatized phospholipids. (J Am Soc Mass Spectrom 2005, 16, 46 -59)

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Negative electrospray ionization low‐energy tandem mass spectrometry of hydroxylated fatty acids: a mechanistic study

Cited by 48 publications

References 26 publications

A new charge-associated mechanism to account for the production of fragment ions in the high-energy CID spectra of fatty acids

A new charge-associated mechanism to account for the production of fragment ions in the high-energy CID spectra of fatty acids

Liquid chromatography/tandem mass spectrometric analysis of 7,10-dihydroxyoctadecenoic acid, its isotopomers, and other 7,10-dihydroxy fatty acids formed byPseudomonas aeruginosa42A2

Total structure characterization of unsaturated acidic phospholipids provided by vicinal di-hydroxylation of fatty acid double bonds and negative electrospray ionization mass spectrometry

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