Kinetics and mechanism of the reaction between hypochlorous acid and tetrathionate ion

Horváth, Attila; Nagypál, Ištván

doi:10.1002/(sici)1097-4601(2000)32:7<395::aid-kin1>3.0.co;2-g

Cited by 22 publications

(24 citation statements)

References 8 publications

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“…Our work builds on previous work showing the cidal effects of electric current on planktonic bacteria ( P. aeruginosa, S. epidermidis, S. gordonii, E. coli, S. aureus ) in solutions and in bacterial biofilms 11,13,22,37–41 . Where our work differs from these earlier works is in (1) developing a useful in vitro agar based platform on which scientific studies may be conducted to determine operating mechanisms for silver-based electroceutical dressings in clinical settings, (2) limiting the current driven through the agar medium, and (3) in determining that the bactericidal effects are due to dissemination of cidal species produced at the electrode.…”

Section: Discussionmentioning

confidence: 72%

“…Anode:accompanied bywhere the first two reactions, are surface-mediated and the electrons are injected into the conduction band of the electrode. The third reaction above can proceed in the forward or reverse direction, but is known to progress in the forward direction at pH values below about 7.5 41 . A corresponding reaction at the cathode is:…”

Section: Discussionmentioning

confidence: 99%

“…This is due to the fact that the third reaction at the anode can be driven left or right depending on the pH of the solution. The pKa of HOCl is 7.53, therefore the reaction should favor production of HOCl and not OCl − since the initial pH of the media is ~7.1 41 . This would result in a smaller change in pH at the anode as compared to the change at the cathode.…”

Section: Discussionmentioning

confidence: 99%

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Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Dusane

Lochab

Jones

et al. 2019

Sci Rep

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Electroceutical wound dressings, especially those involving current flow with silver based electrodes, show promise for treating biofilm infections. However, their mechanism of action is poorly understood. We have developed an in vitro agar based model using a bioluminescent strain of Pseudomonas aeruginosa to measure loss of activity and killing when direct current was applied. Silver electrodes were overlaid with agar and lawn biofilms grown for 24 h. A 6 V battery with 1 kΩ ballast resistor was used to treat the biofilms for 1 h or 24 h. Loss of bioluminescence and a 4-log reduction in viable cells was achieved over the anode. Scanning electron microscopy showed damaged cells and disrupted biofilm architecture. The antimicrobial activity continued to spread from the anode for at least 2 days, even after turning off the current. Based on possible electrochemical ractions of silver electrodes in chlorine containing medium; pH measurements of the medium post treatment; the time delay between initiation of treatment and observed bactericidal effects; and the presence of chlorotyrosine in the cell lysates, hypochlorous acid is hypothesized to be the chemical agent responsible for the observed (destruction/killing/eradication) of these biofilm forming bacteria. Similar killing was obtained with gels containing only bovine synovial fluid or human serum. These results suggest that our in vitro model could serve as a platform for fundamental studies to explore the effects of electrochemical treatment on biofilms, complementing clinical studies with electroceutical dressings.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Dusane

Lochab

Jones

et al. 2019

Sci Rep

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“…Further complicating the matter, in some cases there are mechanistic ambiguities, and in some others the data are limited to a single pH. Two aspects of HOCl chemistry need to be stated at the outset: the species is a weak acid with pK a HOCl = 7.4 at 1 M ionic strength, 22,23 and it readily undergoes comproportionation: 24 (4)…”

Section: Hocl Nuc Nuccl Ohmentioning

confidence: 99%

Oxidations at Sulfur Centers by Aqueous Hypochlorous Acid and Hypochlorite: Cl⁺ Versus O Atom Transfer

Xie

Stanbury

2017

Inorg. Chem.

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Sulfur-containing compounds are known to be susceptible to oxidation by aqueous HOCl, but the factors affecting the rates of these reactions are not well-established. Here we report on the kinetics of oxidation of thiosulfate, thiourea, thioglycolate, (methylthio)acetate, tetrathionate, dithiodiglycolate, and dithiodipropionate at 25 °C and 0.4 M ionic strength. These reactions obey the general rate law -d[OCl]/dt = (k[OCl] + k[HOCl])[substrate] with some exceptions: tetrathionate and the two disulfides undergo rate-limiting hydrolysis at high pH, and dithiodiglycolate has an additional term in the rate law that is second order in [substrate]. The reactions of HOCl are believed to have a Cl transfer mechanism, and in the case of thiosulfate the rate of hydrolysis of the ClSO intermediate was determined. In the case of thiourea evidence was obtained for thiourea monoxide as a long-lived product. It is shown that sulfite and species with terminal sulfur atoms have k values in the vicinity of 1 × 10 M s, while SCN and thioethers react somewhat more slowly; tetrathionate, trithionate, and disulfides react much more slowly. Comparison of the rate constants with those for oxidation of these sulfur substrates by HO and [Pt(CN)Cl] shows that HOCl reacts a few orders of magnitude more rapidly than [Pt(CN)Cl] and ∼9 orders of magnitude more rapidly than HO. Many of the k values are leveled by the high electrophilicity of HOCl. It is proposed that the k values correspond to oxygen-atom transfer mechanisms, as supported by LFERS (linear free energy relationships) relating these rate constants to those for reactions of HO and [Pt(CN)Cl].

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“…Polythionatesespecially trithionate, tetrathionate, and pentathionateare crucial intermediates of redox transformation of sulfur-containing oxyanions in several environmentally and industrially important chemical processes, − and their role is also inevitable in the metabolism of microorganisms. − Despite the fact that these species may play crucial roles in these processes, their reactions seem to be poorly studied, and many kinetic aspects of their reactions are still awaiting clarification. Among the known polythionates, oxidation reactions of tetrathionate are the most studied systems, but besides the ones investigated by our research group, − only a small number of independent studies exist in the literature, such as the detailed study of the tetrathionate–iodine, the tetrathionate–oxygen reaction in the presence of iron(III) catalyst, and that of the tetrathionate–hydroxyl radical reaction . Even less is known about the redox transformation of trithionate and pentathionate; besides the trithionate–iodine, pentathionate–iodine, pentathionate–iodate, and pentathionate–periodate systems, the ferrate(VI)–polythionate reactions were studied systematically by Read et al , Investigation of the redox transformation of polythionates was recently brought into the focus of interest by clarifying the well-known term clock reaction.…”

Section: Introductionmentioning

confidence: 99%

Autocatalytic Oxidation of Trithionate by Iodate in a Strongly Acidic Medium

et al. 2017

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The trithionate-iodate reaction has been studied spectrophotometrically in an acidic medium at 25.0 ± 0.1 °C in phosphoric acid/dihydrogen phosphate buffer, monitoring the absorbance at 468 nm at the isosbestic point of the iodine-triiodide ion system and at I = 0.5 M ionic strength adjusted by sodium perchlorate. The main characteristics of the title system are very reminiscent of those found recently in the pentathionate-iodate and the pentathionate-periodate reactions, the systems paving the way for classifying clock reactions. Thorough analysis revealed that the direct trithionate-iodate reaction plays a subtle role only to produce a trace amount of iodide ion via a finite sequence of reactions, and once its concentration reaches a certain level, then the reaction is almost exclusively governed by the trithionate-iodine and iodide-iodate reactions. The title reaction, as expected, was experimentally proven to be autocatalytic with respect to iodide ion. A simple three-step Landolt-type kinetic model is proposed to describe adequately the most important kinetic features of the title system that can easily be extended to a feasible sequence of elementary and quasi-elementary reactions.

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Kinetics and mechanism of the reaction between hypochlorous acid and tetrathionate ion

Cited by 22 publications

References 8 publications

Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Oxidations at Sulfur Centers by Aqueous Hypochlorous Acid and Hypochlorite: Cl⁺ Versus O Atom Transfer

Autocatalytic Oxidation of Trithionate by Iodate in a Strongly Acidic Medium

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Kinetics and mechanism of the reaction between hypochlorous acid and tetrathionate ion

Cited by 22 publications

References 8 publications

Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Electroceutical Treatment of Pseudomonas aeruginosa Biofilms

Oxidations at Sulfur Centers by Aqueous Hypochlorous Acid and Hypochlorite: Cl+ Versus O Atom Transfer

Autocatalytic Oxidation of Trithionate by Iodate in a Strongly Acidic Medium

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Oxidations at Sulfur Centers by Aqueous Hypochlorous Acid and Hypochlorite: Cl⁺ Versus O Atom Transfer