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Cited by 52Free Radicals and AntioxidantsElectron Spin Resonance StudiesAdvanced oxidation water treatment

Reaction of the superoxide radical with the N-centered radical derived from N-acetyltryptophan methyl ester

Fang, Xingwang, Jin, Faming, Jin, Haofang, Sonntag, Clemens von·1998·Journal of the Chemical Society, Perkin Transactions 2
DOI 10.1039/a706979k
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Abstract

Hydroxyl radicals, solvated electrons and H atoms are generated by pulse radiolysis in aqueous solutions of N-acetyltryptophan methyl ester (AM-Trp). The solvated electrons are converted with N2O into further OH radicals and the latter with azide into N3 radicals which oxidize AM-Trp to its N-centered radical (AM-TrpN˙). It is characterized by a strong absorption at 510 nm (ε = 1830 dm3 mol–1 cm–1). The bimolecular decay of the radicals (2k = 7.3 × 108 dm3 mol–1 s–1) is not affected by O2 [k(AM-TrpN˙ + O2) < 105 dm3 mol–1; 2 × 103 dm3 mol–1 s–1 deduced from other data]. In the presence of O2, and when the majority of the OH radicals are converted with formate into superoxide radicals, O2˙–, decay of the AM-TrpN˙ radicals follows first-order kinetics [k(AM-TrpN˙ + O2˙–) = 1.2 × 109 dm3 mol–1 s–1]. In O2-saturated azide-containing solutions [G(AM-TrpN˙) = 2.9 × 10–7 mol J–1; G(O2˙–) = 3.3 × 10–7 mol J–1] AM-Trp is consumed with a G value of (2.9 ± 0.5) × 10–7 mol J–1, i.e. a restitution of AM-Trp by electron transfer from O2˙– to AM-TrpN˙, although thermodynamically possible [E7(O2˙–) = –0.33 V; E7(TrpN˙) = +1.0 V], must be of very little importance compared to an addition. This has been supported by a product study. The major products are the corresponding N-formylkynurenine (G = 1.4 × 10–7 mol J–1) and two hydroperoxides (total G = 0.7 × 10–7 mol J–1) which to a large extent convert upon standing at room temperature into 1-acetyl-2-methoxycarbonyl-3-hydroxy-1,2,3,8,8-hexahydropyrroloindole (AM-HIP). The same products and product ratios are also formed, when singlet oxygen (from the irradiation of Rose Bengal with visible light) is reacted with AM-Trp suggesting that these two processes lead to the same (short-lived) hydroperoxidic intermediate.

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  • Trp• reacts very rapidly with O2•− with second-order rate constants k in the range 0.7-2.2 × 10^9 M−1 s−1, mainly giving hydroperoxides in almost quantitative yields.

    “Trp• reacts very rapidly with O2•− with second order rate constants, k, in the range 0.7–2.2 × 109 M−1 s−1, the main initial products being hydroperoxides, in almost quantitative yields [145,146,147,148,149,150,151], Figure 56.”

    From Superoxide Anion Chemistry—Its Role at the Core of the Innate Immunity (2023) · cites this paper as [146]

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Authors
Fang, X., Jin, F., Jin, H., & Sonntag, C. V.
Venue
Journal of the Chemical Society, Perkin Transactions 2
Publisher
Royal Society of Chemistry (RSC)
Published
1998
Issue
2
Pages
259-264
ISSN
  • 0300-9580 (ISSN-L)
  • 1364-5471
DOI
10.1039/a706979k
OpenAlex
W2092954618
Cited by
51
References
13
Citations by year
2026: 2 · 2025: 3 · 2024: 1 · 2023: 2 · 2021: 6 · 2020: 4 · 2019: 2 · 2018: 5 · 2017: 2 · 2016: 1 · 2015: 1 · 2014: 1 · 2012: 2
FWCI
1.52
Type
journal article
Language
en
Open access
closed
Locations
Journal of the Chemical Society Perkin Transactions 2 (publishedVersion)
Topics
  • Physical Sciences › Chemistry › Organic Chemistry › Free Radicals and Antioxidants
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biophysics › Electron Spin Resonance Studies
  • Physical Sciences › Environmental Science › Water Science and Technology › Advanced oxidation water treatment
Keywords
superoxide, N-centered radicals, hydroxyl radicals, solvated electrons, N-formylkynurenine, hydroperoxides, electron transfer, reaction kinetics, reaction mechanism, tryptophan oxidation, pulse radiolysis, azide labeling, N2O, formate, oxygen atom transfer

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