Evidence for the Prerequisite Formation of Phenoxyl Radicals in Radical‐Mediated Peptide Tyrosine Nitration In Vacuo

Lai, Cheuk-Kuen; Tang, Wai Kit; Siu, Chi‐Kit; Chu, Ivan K.

doi:10.1002/chem.201904484

Cited by 5 publications

(6 citation statements)

References 28 publications

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“…Finally, in a very elegant example showcasing the power of IMR to uncover hard‐to‐obtain mechanistic insights, the Chu group showed that phenoxyl radicals are the pre‐requisite intermediates in peptide tyrosine nitration by • NO 2 (Lai et al, 2020). By studying the radical cation of the tetrapeptide GGYG the authors saw the evidence of a covalent insertion of NO 2 into the aromatic ring of the Tyr residue (Figure 23):…”

Section: Imr Of Radical Ionsmentioning

confidence: 99%

“…(A) MS spectrum after the ion–molecule reaction of • NO 2 towards [GGYG] •+ ( m /z 352), and B) the CID spectrum of NO 2 [GGYG] + ( m / z 398). (from reference: Lai et al, 2020). [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Imr Of Radical Ionsmentioning

confidence: 99%

“…All energies are in kJ mol −1 . (from reference: Lai et al, 2020). [Color figure can be viewed at wileyonlinelibrary.com]…”

Section: Imr Of Radical Ionsmentioning

confidence: 99%

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Ion‐molecule reactions of mass‐selected ions

Parker

Bollis

Ryzhov

2022

Mass Spectrometry Reviews

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Gas‐phase reactions of mass‐selected ions with neutrals covers a very broad area of fundamental and applied mass spectrometry (MS). Oftentimes, ion‐molecule reactions (IMR) can serve as a viable alternative to collision‐induced dissociation and other ion dissociation techniques when using tandem MS. This review focuses on the literature pertaining applications of IMR since 2013. During the past decade considerable efforts have been made in analytical applications of IMR, including advances in one of the major techniques for characterization of unsaturated fatty acids and lipids, ozone‐induced dissociation, and the development of a new technique for sequencing of large ions, hydrogen atom attachment/abstraction dissociation. Many advances have also been made in identifying gas‐phase chemistry specific to a functional group in organic and biological compounds, which are useful in structure elucidation of analytes and differentiation of isomers/isobars. With “soft” ionization techniques like electrospray ionization having become mainstream for quite some time now, the efforts in the area of metal ion catalysis have firmly moved into exploring chemistry of ligated metal complexes in their “natural” oxidation states allowing to model individual steps of mechanisms in homogeneous catalysis, especially in combination with high‐level DFT calculations. Finally, IMR continue to contribute to the body of knowledge in the area of chemistry of interstellar processes.

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Section: Imr Of Radical Ionsmentioning

confidence: 99%

Section: Imr Of Radical Ionsmentioning

confidence: 99%

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Ion‐molecule reactions of mass‐selected ions

Parker

Bollis

Ryzhov

2022

Mass Spectrometry Reviews

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“…Tyrosyl radicals are relatively stable π‐radicals that play a paramount role in the long‐distance electron transfer found in many important biological systems such as Photosystem II, ribonucleotide reductase (RNR), and cytochrome c oxidase [6] . In Photosystem II, an unclustered, single water molecule is involved in hydrogen atom transfer (HAT) from a tyrosine residue (Tyr161) and stabilization of resulting tyrosyl radicals (Figure 1a) [7] .…”

Section: Introductionmentioning

confidence: 99%

2‐Methoxyethyl Nitrite as a Reagent for Chemoselective On‐Water Nitration

Kitanosono

Hashidoko

Yamashita

et al. 2022

Chemistry An Asian Journal

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An on-water approach has been developed that allows a nitration of tyrosines and phenols under mild conditions. We envisioned that the assembly of tyrosine/ tyrosyl radical couples with interfacial water molecules would realize a biomimetic stacking hydrogen atom transfer (HAT) transition state to facilitate the electron-transfer process. The optimal organic nitrite, 2-methoxyethyl nitrite, resulted in rapid coupling of the tyrosyl radicals with * NO 2 at the oilwater interface to afford the nitrated phenols. Many characteristics found in our on-water strategy are distinct from other complementary systems that include radical nitration. These enticing roles of water in the reaction process introduce new avenues to explore in the design of synthetic organic chemistry systems.

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“…Identifying ortho protein tyrosine nitration (PTN, Scheme S1) is important because this modification is a known biomarker of neurodegenerative disorders and age-related diseases. 23 Furthermore, because nitration is both regioselective and highly selective for specific tyrosyl residues, 24 detection of further endogenous nitration sites may aid in determining the factors that promote nitration. Previously, such identification has been challenging because of the low stoichiometry of PTN modification (estimated occurrence: <0.001%).…”

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confidence: 99%

rPTMDetermine: A Fully Automated Methodology for Endogenous Tyrosine Nitration Validation, Site-Localization, and Beyond

et al. 2020

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We present herein rPTMDetermine, an adaptive and fully automated methodology for validation of the identification of rarely occurring post-translational modifications (PTMs), using a semisupervised approach with a linear discriminant analysis (LDA) algorithm. With this strategy, verification is enhanced through similarity scoring of tandem mass spectrometry (MS/MS) comparisons between modified peptides and their unmodified analogues. We applied rPTMDetermine to (1) perform fully automated validation steps for modified peptides identified from an in silico database and (2) retrieve potential yet-to-be-identified modified peptides from raw data (that had been missed through conventional database searches). In part (1), 99 of 125 3-nitrotyrosyl-containing (nitrated) peptides obtained from a ProteinPilot search were validated and localized. Twenty nitrated peptides were falsely assigned because of incorrect monoisotopic peak assignments, leading to erroneous identification of deamidation and nitration. Five additional nitrated peptides were, however, validated after performing nonmonoisotopic peak correction. In part (2), an additional 236 unique nitrated peptides were retrieved and localized, containing 113 previously unreported nitration sites; 25 endogenous nitrated peptides with novel sites were selected and verified by comparison with synthetic analogues. In summary, we identified and confidently validated 296 unique nitrated peptidescollectively representing the largest number of endogenously identified 3-nitrotyrosyl-containing peptides from the cerebral cortex proteome of a Macaca fascicularis model of stroke. Furthermore, we harnessed the rPTMDetermine strategy to complement conventional database searching and enhance the confidence of assigning rarely occurring PTMs, while recovering many missed peptides. In a final demonstration, we successfully extended the application of rPTMDetermine to peptides featuring tryptophan oxidation.

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Evidence for the Prerequisite Formation of Phenoxyl Radicals in Radical‐Mediated Peptide Tyrosine Nitration In Vacuo

Cited by 5 publications

References 28 publications

Ion‐molecule reactions of mass‐selected ions

Ion‐molecule reactions of mass‐selected ions

2‐Methoxyethyl Nitrite as a Reagent for Chemoselective On‐Water Nitration

rPTMDetermine: A Fully Automated Methodology for Endogenous Tyrosine Nitration Validation, Site-Localization, and Beyond

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