The formation and fragmentation of negative ions derived from organic molecules

Bowie, John H.

doi:10.1002/mas.1280030202

Cited by 129 publications

(50 citation statements)

References 363 publications

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“…In contrast, reduction at either of the carbonyl groups of the phosphocholine ligand would yield the ketyl radical anions C1 and C2. Not only are these species related to the superbase mechanism for ECD [16,17], but based on previous gas-phase [18] and condensed-phase [19] studies on ketyl radical anions, these would be expected to fragment via ␣-cleavage reactions to yield the products shown in eq 8 of Scheme 2.…”

Section: Linear Ion Trap-fourier Transform Ion-cyclotron Resonance Mamentioning

confidence: 99%

Electron capture dissociation of complexes of diacylglycerophosphocholine and divalent metal ions: Competition between charge reduction and radical induced phospholipid fragmentation

James

Perugini

O’Hair

2008

J. Am. Soc. Mass Spectrom.

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Divalent metal complexes of phosphocholines, [Metal II (L)n] 2ϩ (where Metal ϭ Cu 2ϩ , Co 2ϩ , Mg 2ϩ , and Ca 2ϩ , L ϭ 1,2-dihexanoyl-sn-glycero-3-phosphocholine [6:0/6:0GPCho] and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine [16:0/18:1GPCho] and n ϭ 2-5), were formed upon electrospray ionization mass spectrometry (ESI/MS) of 8 mM solution of phosphocholine (L) with 4 mM metal salt (Metal). The electron capture dissociation (ECD) reactions of these [Metal II (L) n ] 2ϩ complexes were examined via Fourier-transform ioncyclotron resonance mass spectrometry. A rich and complex chemistry was observed, including charge reduction and fragmentation involving losses of a methyl radical, trimethylamine, and the acyl chains. The predominant reaction channel was dependent on the size (n) of the complex, the metal and ligand used, and the size of the acyl chain. Thus charge reduction dominates the ECD spectra of the larger phosphocholine, 16:0/18:1GPCho, but is largely absent in the smaller 6:0/6:0GPCho. For complexes of 16:0/18:1GPCho, n ϭ 4 -5, fragmentation from the head group mainly occurs via loss of the methyl radical and trimethylamine. At n ϭ 3, the relative abundance of fragments due to loss of acyl chain radicals increases. The abundances of ions arising from these radical losses increase further for the n ϭ 2 complexes, thereby providing information on the composition and position of the 16:0 and 18:1 acyl groups. Thus ECD of metal complexes provides structurally useful information on the phosphocholine, including the nature of the head group, the acyl chains, and the positions of the acyl chains. complexes of L ϭ 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, which allows distinction of acyl chains [9]. We were thus intrigued by the possibility of using electron capture dissociation (ECD) on divalent metal complexes of phospholipids to gain additional structural information, since recent studies suggest that divalent metal ions not only can direct the fragmentation of peptides under conditions of ECD [10 -13], but also act as charge tags to allow the use of ECD on other biomolecules that may not undergo multiple protonation under electrospray ionization (ESI) conditions [13].

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Section: Linear Ion Trap-fourier Transform Ion-cyclotron Resonance Mamentioning

confidence: 99%

Electron capture dissociation of complexes of diacylglycerophosphocholine and divalent metal ions: Competition between charge reduction and radical induced phospholipid fragmentation

James

Perugini

O’Hair

2008

J. Am. Soc. Mass Spectrom.

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“…The loss of a neutral alkyl radical from alkyl aryl ether negative ions by homolytic fission is a wellknown favorable fragmentation reaction in the gas phase. 31 (…”

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Mass Spectrometry-Based Fragmentation as an Identification Tool in Lignomics

et al. 2010

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The ensemble of all phenolics for which the biosynthesis is coregulated with lignin biosynthesis, i.e., metabolites from the general phenylpropanoid, monolignol, and (neo)-lignan biosynthetic pathways and their derivatives, as well as the lignin oligomers, is coined the lignome. In lignifying tissues, the lignome comprises a significant portion of the metabolome. However, as is true for metabolomics in general, the structural elucidation of unknowns represents the biggest challenge in characterizing the lignome. To minimize the necessity to purify unknowns for NMR analysis, it would be desirable to be able to extract structural information from liquid chromatography-mass spectrometry data directly. However, mass spectral libraries for metabolomics are scarce, and no libraries exist for the lignome. Therefore, elucidating the gas-phase fragmentation behavior of the major bonding types encountered in lignome-associated molecules would considerably advance the systematic characterization of the lignome. By comparative MS n analysis of a series of molecules belonging to the -aryl ether, benzodioxane, phenylcoumaran, and resinol groups, we succeeded in annotating typical fragmentations for each of these bonding structures as well as fragmentations that enabled the identification of the aromatic units involved in each bonding structure. Consequently, this work lays the foundation for a detailed characterization of the lignome in different plant species, mutants, and transgenics and for the MS-based sequencing of lignin oligomers and (neo)lignans.Lignin is an aromatic heteropolymer that is mainly present in secondary-thickened plant cell walls where it provides the necessary strength and hydrophobicity for plants to grow in an upward direction and to enable the transport of water, nutrients, and photoassimilates. Lignin is mainly composed of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units derived from the combinatorial coupling of p-coumaryl, coniferyl, and sinapyl alcohols ( Figure 1A), 1 the so-called monolignols that are produced by the general phenylpropanoid and monolignol biosynthetic pathways. [2][3][4][5] Following oxidation by peroxidase and/or laccase, the resulting electron-delocalized monolignol radical has unpaired electron density at its 1-, 3-, O-4-, 5-, and 8-positions ( Figure 1B). As radical coupling at the 8-position is favored, coupling with another monolignol radical results in, after rearomatization, a mixture of dehydrodimers with 8-8′, 8-5′, and 8-O-4′ linkages ( Figure 1C).In addition to these major monomers, several other monomers have been identified in particular species or in plants with modified lignin biosynthesis, 1,3 such as 5-hydroxyconiferyl alcohol in caffeic acid O-methyltransferase (COMT) downregulated transgenic plants, 6,7 dihydroconiferyl alcohol in cinnamyl alcohol dehydrogenase (CAD) deficient loblolly pine, 8 acylated monolignols, such as sinapyl p-hydroxybenzoate in poplar, 9 and hydroxycinnamic acid or hydroxycinnamate esters, such as feruloyl tyramine in tobacco....

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“…The presence of acidic groups such as carboxyl functions are preferred ionization sites, initiating determined fragmentation routes of the negatively charged molecule [24,25]. The derivatization of those functionalities to methyl esters, for instance, entails the preference of other, formerly less acidic hydrogens to be abstracted from the analyte being responsible for the generation of its anion and causing a different dissociation scheme.…”

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Effect of the location of hydrogen abstraction on the fragmentation of diuretics in negative electrospray ionization mass spectrometry

Thevis

Schänzer

Schmickler

2003

J. Am. Soc. Mass Spectrom.

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The diuretic agents bumetanide, xipamide, indapamide, and related compounds were investigated in order to determine the effect of different ionization sites on their collisionally activated dissociation and the corresponding fragmentation pathways. Therefore, analytes were selectively alkylated, and structural analogues as well as deuterium labeled compounds synthesized, which contain a reduced number of ionizable hydrogen atoms. Thus, specific hydrogen abstractions and their correlated dissociation routes of the negatively charged molecules were eliminated, providing evidence for the influence of the location of ionization on product ion spectra. Fragment ions such as m/z 78 indicate ionization at the commonly present sulfamoyl residue of diuretics but does not exclude additional ionization sites. Product ion spectra of the investigated diuretic agents proved to be composed by fragmentations initiated from different hydrogen abstractions. Moreover, the generation of radical anions by collision-activated dissociation of even-electron precursor ions was observed, the generation of which is discussed by proposed fragmentation pathways. (J Am Soc Mass Spectrom 2003, 14, 658 -670)

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The formation and fragmentation of negative ions derived from organic molecules

Cited by 129 publications

References 363 publications

Electron capture dissociation of complexes of diacylglycerophosphocholine and divalent metal ions: Competition between charge reduction and radical induced phospholipid fragmentation

Electron capture dissociation of complexes of diacylglycerophosphocholine and divalent metal ions: Competition between charge reduction and radical induced phospholipid fragmentation

Mass Spectrometry-Based Fragmentation as an Identification Tool in Lignomics

Effect of the location of hydrogen abstraction on the fragmentation of diuretics in negative electrospray ionization mass spectrometry

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