Reaction of superoxide radicals with glycosaminoglycan chloramides: a kinetic study

Parsons, Barry J.; Sibanda, Sambulelwe; Heyes, Derren J.; Paterson, Andrew W.J.

doi:10.1016/j.freeradbiomed.2013.03.011

Cited by 10 publications

(8 citation statements)

References 54 publications

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“…However, not all biologically relevant radicals induce GAG chain breaks. In a laser flash photolysis study (performed at pH = 8.5), the reaction between O 2 and HA or heparin only showed O 2 dismutation, implying very low or no reactivity of O 2 toward these GAGs (109). Subsequent fragmentation studies confirmed the lack of reactivity and (direct) GAG fragmentation by O 2 -(132).…”

Section: Mechanisms Of Gcx Oxidationmentioning

confidence: 87%

The Mechanisms and Physiological Relevance of Glycocalyx Degradation in Hepatic Ischemia/Reperfusion Injury

Golen

Reiniers

Vrisekoop

et al. 2014

Antioxidants & Redox Signaling

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Section: Mechanisms Of Gcx Oxidationmentioning

confidence: 87%

The Mechanisms and Physiological Relevance of Glycocalyx Degradation in Hepatic Ischemia/Reperfusion Injury

Golen

Reiniers

Vrisekoop

et al. 2014

Antioxidants & Redox Signaling

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“…It is thus difficult at present to reconcile the kinetic data [42], the SOTS-1 studies [23,27] and the fragmentation data presented here. It may be that superoxide reduces the chloramide directly, as confirmed for other reducing radicals in the previous kinetic study [41] to produce the amidyl radical which may react rapidly with oxygen to produce a nitroxide species as found in previous studies of sterically-hindered amidyl and aminyl radicals [43,44].…”

Section: Resultsmentioning

confidence: 63%

“…The weak reducing agent, the superoxide radical was produced by the irradiation of oxygen-saturated 0.1mM and 0.8mM chloramide ( HACl) and 0.4mM chloramide (HepCl ) solutions containing 0.1M formate at pH 9.5, as in reactions (1) and (3) [42]. Despite this demonstration of a reaction, it would appear from the current study that it does not lead to fragmentation of HACl.…”

Section: Resultsmentioning

confidence: 63%

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Efficiencies of fragmentation of glycosaminoglycan chloramides of the extracellular matrix by oxidizing and reducing radicals: potential site-specific targets in inflammation?

Sibanda

Akeel

Martin

et al. 2013

Free Radical Biology and Medicine

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Hypochlorous acid and its conjugate base, hypochlorite ions, produced in inflammatory conditions, may produce chloramides of glycosaminoglycans, the latter being significant components of the extracellular matrix (ECM). This may occur through the binding of myeloperoxidase directly to the glycosaminoglycans. The N-Cl group in the chloramides is a potential selective target for both reducing and oxidising radicals, leading possibly to more efficient and damaging fragmentation of these biopolymers relative to the parent glycosaminoglycans. To investigate the effect of the N-Cl group, ionising radiation has been used to produce quantifiable concentrations of the reducing radicals, the hydrated electron and the superoxide radical and also of the oxidizing radicals, hydroxyl, carbonate and nitrogen dioxide, all of which have been reacted with hyaluronan and heparin and their chloramides in the current study . PAGE gels calibrated for molecular weight have allowed the consequent fragmentation efficiencies of these radicals to be calculated.Hydrated electrons were shown to produce fragmentation efficiencies of 100% and 25 % for hyaluronan chloramide (HACl) and heparin chloramide (HepCl), respectively. The role of the sulphate group in heparin in the reduction of fragmentation can be rationalized using mechanisms proposed by Davies and co-workers (Rees et al. J. Am. Chem. Soc. 125: 13719-13733; in which the initial formation of an amidyl radical leads rapidly to a C-2 radical on the glucosamine moiety. The latter is 100% efficient in causing glycodsidic bond breakage in HACl but only 25 % in HepCl, the role of the sulphate group being to favour the non-fragmentory routes for the C-2 radical. The weaker reducing agent, the superoxide radical, did not cause fragmentation of either HACl or HepCl although kinetic reactivity had been demonstrated in earlier studies. 3Experiments using the oxidizing radicals, hydroxyl and carbonate, both potential in vivo species, show significant increases in fragmentation efficiencies for both HACl and HepCl, relative to the parent molecules. The carbonate radical has been shown to be involved in site-specific reactions at the N-Cl groups, reacting via abstraction of Cl, to produce the same amidyl radical produced by one-electron reductants such as the hydrated electron. As for the hydrated electrons, the data support fragmentation efficiencies of 100% and 29% for reaction of carbonate radicals at N-Cl for HACl and HepCl respectively. For the weaker oxidant, nitrogen dioxide, no fragmentation was observed, probably attributable to a low kinetic reactivity and low reduction potential.It seems likely therefore that the N-Cl group can direct damage to extracellular matrix glycosaminoglycan chloramides which may be produced under inflammatory conditions.The in vivo species , the carbonate radical is also much more likely to be site-specific in its reactions with such components of the ECM than the hydroxyl radical. Graphical abstract4

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“…[33][34][35][36][37][38][39][40] Due to its outstanding oxidative power, this species can significantly alter the activities and availabilities of biomolecules.…”

Section: Introductionmentioning

confidence: 99%

The kinetics and mechanism of the oxidation of pyruvate ion by hypochlorous acid

et al. 2015

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The oxidation of pyruvic acid by hypochlorous acid was studied in the pH 1.0 -11.0 range. The main path in the redox process is the reaction between the pyruvate ion and HOCl. It was shown that the reaction is second order in both reactants and kHOCl = 2.14 ± 0.02M −1 s −1 (I = 1.0 M (NaClO4), T = 25.0 °C) with ∆HHOCl ≠ = 34.6 ± 1.2 kJmol −1 and ∆SHOCl ≠ = −120.3 ± 3.6 Jmol −1 K −1 for this reaction step. The relatively large negative entropy of activation is consistent with an O atom-transfer mechanism. DFT calculations support this conclusion by predicting a concerted rearrangement of the activated complex which includes the reactants and the solvent water molecule. It was also confirmed that the hydration of pyruvic acid has significant contribution to the observed kinetic features under acidic condition. The hydration reaction is a proton catalyzed process and the pseudo-first order rate constant can be interpreted by considering theprotolytic and hydration equilibria of pyruvic acid. The rate constants were determined for the non-catalytic and the proton catalyzed path: kh0 = 0.24 ± 0.01 s −1 and kh1 = 5.5 ± 0.2 M −1 s −1 .

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Reaction of superoxide radicals with glycosaminoglycan chloramides: a kinetic study

Cited by 10 publications

References 54 publications

The Mechanisms and Physiological Relevance of Glycocalyx Degradation in Hepatic Ischemia/Reperfusion Injury

The Mechanisms and Physiological Relevance of Glycocalyx Degradation in Hepatic Ischemia/Reperfusion Injury

Efficiencies of fragmentation of glycosaminoglycan chloramides of the extracellular matrix by oxidizing and reducing radicals: potential site-specific targets in inflammation?

The kinetics and mechanism of the oxidation of pyruvate ion by hypochlorous acid

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