20103-10-0Relevant articles and documents
Characterization of chlorinated adducts of hemoglobin and albumin following administration of pentachlorophenol to rats
Waidyanatha, Suramya,Lin, Po-Hsiung,Rappaport, Stephen M.
, p. 647 - 653 (1996)
Five cysteinyl adducts (including one with multiple isomeric forms) of hemoglobin (Hb) and albumin (Alb) have been characterized in the blood of Sprague-Dawley rats following administration of pentachlorophenol (PCP). Three of these adducts were formed by multiple substitution reactions of tetrachloro-1,4-benzoquinone (Cl4-1,4-BQ) and its products, and two arose from reactions of tetrachloro-1,4-benzosemiquinone (Cl4-1,4-SQ) and tetrachloro-1,2-benzosemiquinone (Cl4-1,2-SQ). Adducts of tetrachloro-1,2- benzoquinone (Cl4-1,2-BQ) were not observed. Regarding adducts of Cl4-1,4- BQ and its products, specific structures were assigned to monosubstituted, disubstituted, and trisubstituted adducts of Hb and Alb following modification of rat blood with Cl4-1,4-BQ (0-45 μM) in vitro and after metabolism of PCP (0-40 mg/kg body weight) in Sprague-Dawley rats, in vivo. The formation of all adducts was linear over the ranges tested, with Alb adducts being more abundant than Hb adducts. The levels of the adducts measured were in the following order: monosubstituted > disubstituted > trisubstituted. The observation that Cl4-1,4-BQ can produce multisubstituted adducts with proteins suggests that protein-protein cross links may be formed, with inherent toxicological implications. Regarding adducts of the semiquinones (detected only in vivo), linear production of Hb and Alb adducts was observed with increasing dosage of PCP for adducts of both Cl41,4-SQ and Cl4-1,2-SQ. Higher levels of the semiquinone adducts were observed in Hb than in Alb, in contrast to the results with the quinone adducts. In a separate in vivo experiment (20 mg PCP/kg body weight), where animals were sacrificed at intervals up to 336 h postadministration, adducts were eliminated at rates which were comparable among the different adducts of a given protein.
Photoaccelerated oxidation of chlorinated phenols
Lente, Gabor,Espenson, James H.
, p. 1162 - 1163 (2003)
Exposure to visible light increases the rate of oxidation of chlorinated phenols by hydrogen peroxide in aqueous solution in either the presence or the absence of iron-based catalysts, which may be explained by the aqueous photoreactions of chloroquinone intermediates.
Light induced elimination of mono- and polychlorinated phenols from aqueous solutions by PW12O403-. The case of 2,4,6-trichlorophenol
Papaconstantinou,Androulaki,Minero,Androulaki,Dimotikali,Pelizzetti,Hiskia
, p. 2024 - 2028 (2000)
PW12O403- was used as catalyst in the photodegradation of polychlorinated phenols (2,4-dichlorophenol (2,4-DCP), 2,6-dichlorophenol (2,6-DCP), 3,4-dichlorophenol (3,4-DCP), 3,5-dichlorophenol (3,5-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP)). Photolysis in 270-290 nm led to the photodecomposition of chlorophenols while the addition of PW12O403- to oxygenated solutions accelerated the photodecomposition. Chlorination of phenol generally enhanced photodecomposition rates while the effect of chlorine substituents in the ortho position was less pronounced. A detailed study of 2,4,6-TCP photodecomposition showed that the major reactions involved hydroxylation of the aromatic ring, substitution of chlorine by OH, oxidation of chlorinated HQ to the corresponding quinone, and breaking of the aromatic ring to produce carboxylic acids, such as maleic, oxalic, acetic and formic acids. The ultimate products were CO2, H2O and Cl-.
Geometrically specific hydrogen transfer in the reaction of terminally alkyl-substituted 1,3-dienes with 1,4-quinones
Cameron, Donald W.,Heisey, Ross M.
, p. 109 - 121 (2000)
Reaction of certain geometrically defined 1,1-dioxy-4-alkyl- and -4,4-dialkyl-substituted buta-l,3-dienes with halogenated quinones does not involve Diels-Alder or Michael addition chemistry. Instead, rapid competitive oxidation of the dienes to give 2,4-dienoate esters was observed. This new reaction involves strong spatial association between diene and quinone, hydrogen being transferred specifically from the (4E)-alkyl group. Its scope is compared with addition of the same terminally substituted dienes towards the reactive non-quinonoid dienophile tetracyanoethylene. CSIRO 2000.
Electrochemical oxidation of diclofenac on CNT and M/CNT modified electrodes
Ferreira, M.,Figueiredo, J. L.,Fonseca, A. M.,Güney, S.,Ku?niarska-Biernacka, I.,Neves, I. C.,Parpot, P.,Pereira, M. F. R.,Soares, O. S. G. P.
, p. 12622 - 12633 (2021/07/25)
The electrochemical oxidation of diclofenac (DCF), a non-steroidal anti-inflammatory drug considered as an emerging pollutant (frequently detected in wastewater), was investigated on CNT, Pt/CNT and Ru/CNT modified electrodes based on Carbon Toray in aqueous media. The electroreactivity of DCF on these modified electrodes was studied using cyclic voltammetry and the kinetic parameters were calculated from the scan rate study. Cyclic voltammograms show several oxidation processes, which confirm the interaction between DCF and the catalyst surface necessary for direct oxidation processes. Constant potential electrolysis of DCF was carried out on carbon nanotubes (CNT) and metal supported CNT (M/CNT) modified electrodes, in 0.1 M NaOH and 0.1 M Na2CO3/NaHCO3buffer media. The highest DCF conversion (88% after 8 h of electrolysis) was found in carbonate buffer medium, for Ru/CNT, while the best carbon mineralization efficiency (corresponding to 48% of the oxidized DCF) was obtained on Pt/CNT modified electrode in 0.1 M NaOH medium. The products of the electrolyses were identified and quantified by HPLC-MS, GC-MS, HPLC-UV-RID and IC. The results show the presence of some low molecular weight carboxylic acids, confirming the cleavage of the aromatic rings during the oxidation process.
Kinetic mechanism of the dechlorinating flavin-dependent monooxygenase HadA
Pimviriyakul, Panu,Thotsaporn, Kittisak,Sucharitakul, Jeerus,Chaiyen, Pimchai
, p. 4818 - 4832 (2017/04/03)
The accumulation of chlorophenols (CPs) in the environment, due to their wide use as agrochemicals, has become a serious environmental problem. These organic halides can be degraded by aerobic microorganisms, where the initial steps of various biodegradation pathways include an oxidative dechlorinating process in which chloride is replaced by a hydroxyl substituent. Harnessing these dechlorinating processes could provide an opportunity for environmental remediation, but detailed catalytic mechanisms for these enzymes are not yet known. To close this gap, we now report transient kinetics and product analysis of the dechlorinating flavin-dependent monooxygenase, HadA, from the aerobic organism Ralstonia pickettii DTP0602, identifying several mechanistic properties that differ from other enzymes in the same class. We first overexpressed and purified HadA to homogeneity. Analyses of the products from single and multiple turnover reactions demonstrated thatHadAprefers 4-CP and 2-CP over CPs with multiple substituents. Stopped-flow and rapid-quench flow experiments of HadA with 4-CP show the involvement of specific intermediates (C4a-hydroperoxy-FAD and C4a-hydroxy-FAD) in the reaction, define rate constants and the order of substrate binding, and demonstrate that the hydroxylation step occurs prior to chloride elimination. The data also identify the non-productive and productive paths of the HadA reactions and demonstrate that product formation is the rate-limiting step. This is the first elucidation of the kinetic mechanism of a two-component flavin-dependent monooxygenase that can catalyze oxidative dechlorination of various CPs, and as such it will serve as the basis for future investigation of enzyme variants that will be useful for applications in detoxifying chemicals hazardous to human health.
