Primary steps in the reactions of organic disulfides with hydroxyl radicals in aqueous solution

Bonifacic, M.; Schaefer, K.; Moeckel, H.; Asmus, K.‐D.

doi:10.1021/j100582a003

Cited by 84 publications

(24 citation statements)

References 4 publications

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“…), the rate of its reaction with • OH is under diffusion control (10); thus, its conversion to other sulfur compounds directly impacts the steady state of -SS-/-SH redox system. It is believed that, in aqueous solutions, single-electron oxidation of the disulfide bond followed by bond cleavage into -S • and -S + is the dominant pathway by which • OH reacts with disulfide bonds (14,15). The disulfide cleavage products can further react with O 2 , • OH, OH − , or other ROS, forming a series of oxyacids of sulfur, including sulfenic acid (-SOH), sulfinic acid (-SO 2 H), and sulfonic acid (-SO 3 H) (3).…”

Section: •−mentioning

confidence: 99%

Two-step reaction mechanism reveals new antioxidant capability of cysteine disulfides against hydroxyl radical attack

Adhikari

Crehuet

Anglada

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Cysteine disulfides, which constitute an important component in biological redox buffer systems, are highly reactive toward the hydroxyl radical (•OH). The mechanistic details of this reaction, however, remain unclear, largely due to the difficulty in characterizing unstable reaction products. Herein, we have developed a combined approach involving mass spectrometry (MS) and theoretical calculations to investigate reactions of •OH with cysteine disulfides (Cys–S–S–R) in the gas phase. Four types of first-generation products were identified: protonated ions of the cysteine thiyl radical (+Cys–S•), cysteine (+Cys–SH), cysteine sulfinyl radical (+Cys–SO•), and cysteine sulfenic acid (+Cys–SOH). The relative reaction rates and product branching ratios responded sensitively to the electronic property of the R group, providing key evidence to deriving a two-step reaction mechanism. The first step involved •OH conducting a back-side attack on one of the sulfur atoms, forming sulfenic acid (–SOH) and thiyl radical (–S•) product pairs. A subsequent H transfer step within the product complex was favored for protonated systems, generating sulfinyl radical (–SO•) and thiol (–SH) products. Because sulfenic acid is a potent scavenger of peroxyl radicals, our results implied that cysteine disulfide can form two lines of defense against reactive oxygen species, one using the cysteine disulfide itself and the other using the sulfenic acid product of the conversion of cysteine disulfide. This aspect suggested that, in a nonpolar environment, cysteine disulfides might play a more active role in the antioxidant network than previously appreciated.

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Section: •−mentioning

confidence: 99%

Two-step reaction mechanism reveals new antioxidant capability of cysteine disulfides against hydroxyl radical attack

Adhikari

Crehuet

Anglada

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Reaction of CO •− 2 with SeCys, SeA, and MeSeP produced transients absorbing in the range of 420-460 nm. From another independent studies and in analogy with pulse radiolysis of disulfides 11 , the transient formed on one electron reduction of the above diselenides has been assigned to be the selenyl radical (RSe • ) produced by the reactions given below [Equations (3,4)]. …”

Section: Pulse Radiolysis Studiesmentioning

confidence: 99%

Correlating the GPx Activity of Selenocystine Derivatives with One-Electron Redox Reactions

Mishra

Barik

Kunwar

et al. 2008

Phosphorus, Sulfur, and Silicon and the Related Elements

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With an aim to develop water soluble, less toxic glutathione peroxidase (GPx) mimics, three selenocystine (SeCys) derivatives, viz., selenocystamine (SeA), diselenodipropionic acid (SeP), and methyl ester of diselenodipropionic acid (MeSeP) have been synthesized and examined for GPx activity along with SeCys. The GPx activity of the compounds was found to be in the order SeCys ∼ = SeA > MeSeP > SeP. The relative affinity of these GPx mimics towards the substrates thiol and hydroperoxide were determined by Lineweaver-Burk (L-B) plots. Since the enzyme activity involves several steps of reduction and oxidation reactions, attempts have been made to understand the role of such processes in deciding the efficacy of diselenides as GPx mimics. For this, one-electron redox chemistry of these compounds was studied in aqueous solutions at pH 7 using nanosecond pulse radiolysis technique. From these studies, it was concluded that SeCys and SeA, which can undergo easy one-electron reduction, exhibit high GPx activity.

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“…It is known that HO  radicals react with the sulfur atom of a thioether to ultimately yield an intermediary sulfur radical cation ( Fig. 17 and 18) 51,52 . Such species are known to undergo two reaction pathways: (1) dimerization with a second nonoxidized thioether (Fig.…”

Section: Product Formation Frommentioning

confidence: 99%

Neighboring amide participation in the Fenton oxidation of a sulfide to sulfoxide, vinyl sulfide and ketone relevant to oxidation of methionine thioether side chains in peptides

et al. 2016

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Oxidation of Met affects the stability of proteins, and was identified as a step in the beta amyloid-dependent pathogenesis of Alzheimer's disease. One-electron oxidation of Met is facilitated through stabilization of sulfide radical cations with electron-rich heteroatoms. The formation of such 2-center-3-electron bonds, formed between sulfide radical cations and amides, leads to pronounced product selectivity during biologically relevant oxidation conditions. Conformationally constrained methionine analogs embedded within a norbornane framework, i.e., 2,6-endo, endo-and 2,6-exo, endo-pyrrolidine amide thiomethyl bicyclo[2.2.1]heptanes

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Primary steps in the reactions of organic disulfides with hydroxyl radicals in aqueous solution

Cited by 84 publications

References 4 publications

Two-step reaction mechanism reveals new antioxidant capability of cysteine disulfides against hydroxyl radical attack

Two-step reaction mechanism reveals new antioxidant capability of cysteine disulfides against hydroxyl radical attack

Correlating the GPx Activity of Selenocystine Derivatives with One-Electron Redox Reactions

Neighboring amide participation in the Fenton oxidation of a sulfide to sulfoxide, vinyl sulfide and ketone relevant to oxidation of methionine thioether side chains in peptides

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