Hydrogen Radical Removal Causes Complex Overlapping Isotope Patterns of Aromatic Carboxylic Acids in Negative-ion Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Yamagaki, Tohru; Watanabe, Takeshi

doi:10.5702/massspectrometry.a0005

Cited by 10 publications

(22 citation statements)

References 9 publications

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“…From the view point of organic chemistry, we assumed that the phenolic OH at the 2‐position interacts with the carboxy group in DHBs according to neighboring group participation as salicylic acid (Supporting Information‐1). The numbers of the [M–2H] •– and [M–3H] − ions observed in six DHB isomers can be explained from their structures with or without the ortho phenolic OH . The ortho phenolic OH groups of 2,3‐DHB, 2,4‐DHB and 2,5‐DHB interact with the carboxy group, and one hydrogen radical is removed from the other phenolic OH group (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Until now, the mechanism of the ion formation of these odd‐electron anions have not been studied. We have studied the hydrogen radical removing ions (the odd‐electron anion [M–2H] •– and [M–3H] − ) of polyphenol compounds such as DHB and flavonoids, and the hydrogen radical can be removed from the phenolic hydroxyl groups …”

mentioning

confidence: 99%

“…[13] Recently, we reported that the ion signal of odd-electron anions ([M-2H] •-) from 2,5-DHB was found to be largest among the DHB positional isomers. [16] It was detected from 2,5-DHB, besides the conventional even-electron anion [M-H] À , as a rare case among all matrices. [6] Until now, the mechanism of the ion formation of these odd-electron anions have not been studied.…”

mentioning

confidence: 99%

“…[6] Until now, the mechanism of the ion formation of these odd-electron anions have not been studied. We have studied the hydrogen radical * [16,17] There was a phenolic OH group from which the hydrogen radical could not removed. We proposed that the hydrogen radical could not be removed from the phenolic OH groups in intramolecular interactions.…”

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confidence: 99%

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Mechanism for odd‐electron anion generation of dihydroxybenzoic acid isomers in matrix‐assisted laser desorption/ionization mass spectrometry with density functional theory calculations

Yamagaki

Takeuchi

Watanabe

et al. 2016

Rapid Comm Mass Spectrometry

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RationaleProton and radical are transferred between matrices and matrix and analyte in matrix‐assisted laser desorption/ionization (MALDI) and these transfers drive ionization of analytes. The odd‐electron anion [M–2H]•– was generated in dihydroxybenzoic acids (DHBs) and the ion abundance of the 2,5‐DHB was the highest among six DHB isomers. We were interested in the mechanism of the ion generation of the odd‐electron anion.MethodsThe observed [M–2H]•– and [M–3H]− ions, which were generated with the hydrogen radical removed from the phenolic hydroxyl groups (OH) in DHB isomers, were analyzed using negative‐ion MALDI‐MS. The enthalpy for ion generation and their stable structures were calculated using the density functional theory (DFT) calculation program Gaussian 09 with the B3LYP functional and the 6–31+G(d) basis set.ResultsThe number of observed [M–2H]•– and [M–3H]− ions of the DHB isomers was dependent on the positions of the phenolic OH groups in the DHB isomers because the carboxy group interacts with the ortho OH group due to neighboring group participation, as confirmed from the stable structures of the [M–2H]•– anions calculated with the Gaussian 09 program. The DHB isomers were placed into three categories according to the number of the ions.ConclusionsOdd‐electron anions ([M–2H]•–) and [M–2H•–H]− ([M–3H]−) ions were generated from DHB isomers due to removal of the hydrogen radical from the phenolic groups. The enthalpy for ion generation revealed that ion formation proceeds via a two‐step pathway through the [M–M]− ion as an intermediate. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.

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confidence: 99%

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confidence: 99%

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Mechanism for odd‐electron anion generation of dihydroxybenzoic acid isomers in matrix‐assisted laser desorption/ionization mass spectrometry with density functional theory calculations

Yamagaki

Takeuchi

Watanabe

et al. 2016

Rapid Comm Mass Spectrometry

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“…These are potentially misinterpreted as a single isotope cluster affecting downstream analyses. This necessitates the deconvolution of the overlapping isotope cluster into at least two valid isotope clusters; Third, substances can be affected by hydrogen loss as reported in [27] and exploited in [28]. This leads to mass differences similar to isotope peaks (

mass (^{1} H)

= 1.008 ≈ 1.0034 = mass

(^{13} C)

− mass

(^{12} C)

) and results in a small trailing peak which is potentially misinterpreted as monoisotopic peak of the putative isotope cluster.…”

Section: Resultsmentioning

confidence: 99%

Prediction, Detection, and Validation of Isotope Clusters in Mass Spectrometry Data

Treutler

Neumann

2016

Metabolites

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Mass spectrometry is a key analytical platform for metabolomics. The precise quantification and identification of small molecules is a prerequisite for elucidating the metabolism and the detection, validation, and evaluation of isotope clusters in LC-MS data is important for this task. Here, we present an approach for the improved detection of isotope clusters using chemical prior knowledge and the validation of detected isotope clusters depending on the substance mass using database statistics. We find remarkable improvements regarding the number of detected isotope clusters and are able to predict the correct molecular formula in the top three ranks in 92% of the cases. We make our methodology freely available as part of the Bioconductor packages xcms version 1.50.0 and CAMERA version 1.30.0.

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Laser-Induced Hydrogen Radical Removal in UV MALDI-MS Allows for the Differentiation of Flavonoid Monoglycoside Isomers

Yamagaki

Watanabe

Tanaka

et al. 2013

J. Am. Soc. Mass Spectrom.

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Negative-ion matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectra and tandem mass spectra of flavonoid mono-O-glycosides showed the irregular signals that were 1 and/or 2 Da smaller than the parent deprotonated molecules ([M – H]–) and the sugar-unit lost fragment ions ([M – Sugar – H]–). The 1 and/or 2 Da mass shifts are generated with the removing of a neutral hydrogen radical (H*), and/or with the homolytic cleavage of the glycosidic bond, such as [M – H* – H]–, [M – Sugar – H* – H]–, and [M – Sugar – 2H* – H]–. It was revealed that the hydrogen radical removes from the phenolic hydroxy groups on the flavonoids, not from the sugar moiety, because the flavonoid backbones themselves absorb the laser. The glycosyl positions depend on the extent of the hydrogen radical removals and that of the homolytic cleavage of the glycosidic bonds. Flavonoid mono-glycoside isomers were distinguished according to their TOF MS and tandem mass spectra.FigureᅟElectronic supplementary materialThe online version of this article (doi:10.1007/s13361-013-0764-0) contains supplementary material, which is available to authorized users.

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Hydrogen Radical Removal Causes Complex Overlapping Isotope Patterns of Aromatic Carboxylic Acids in Negative-ion Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Cited by 10 publications

References 9 publications

Mechanism for odd‐electron anion generation of dihydroxybenzoic acid isomers in matrix‐assisted laser desorption/ionization mass spectrometry with density functional theory calculations

Mechanism for odd‐electron anion generation of dihydroxybenzoic acid isomers in matrix‐assisted laser desorption/ionization mass spectrometry with density functional theory calculations

Prediction, Detection, and Validation of Isotope Clusters in Mass Spectrometry Data

Laser-Induced Hydrogen Radical Removal in UV MALDI-MS Allows for the Differentiation of Flavonoid Monoglycoside Isomers

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