697-91-6Relevant articles and documents
Kinetic study of the oxidative dehalogenation of 2,4,6-trichlorophenol catalyzed by chloroperoxidase
Diaz-Diaz, Goretti,Blanco-Lopez, M. Carmen,Lobo-Castanon, M. Jesus,Miranda-Ordieres, Arturo J.,Tunon-Blanco, Paulino
, p. 332 - 336 (2010)
A sigmoidal behaviour of chloroperoxidase for the oxidative dehalogenation of 2,4,6-trichlorophenol is reported for the first time. Kinetic data were adjusted to the Hill equation and the kinetic parameters were obtained: n = 1.7±0.2, vmax =(8.8±0.3) × 10 -5Mmin-1, the pseudo-Michaelis constant Ks * = (8.6±0.5) × 10-5 M, kcat = 677±84min-1 and the catalytic efficiency = (8.9 ±0.6) × 106M-1 min-1. The sigmoidal curve could be related to the cooperative binding of the substrate to the enzyme, so that the binding of the first substrate molecule may help the binding of the second one. Further, both substrate molecules could establish Π-Π interactions between them, which would confer more stability to the system.
Unusual kinetic role of a water-soluble iron(III) porphyrin catalyst in the oxidation of 2,4,6-trichlorophenol by hydrogen peroxide
Lente, Gabor,Espenson, James H.
, p. 449 - 455 (2004)
The oxidation of 2,4,6-trichlorophenol (TCP) to 2,6-dichloro-1,4-benzoquinone (DCQ) by hydrogen peroxide using iron(III) meso-tetra(4-sulfonatophenyl) porphine chloride, Fe(TPPS)Cl, as a catalyst was studied with stopped-flow UV-vis spectrophotometry and potentiometry using a chloride ion selective electrode. The observations are interpreted by a three-step kinetic model: the initial reaction of the catalyst with the oxidant (Fe(TPPS)+ + H2O2 → Cat′) produces an active intermediate, which oxidizes the substrate (Cat′ + TCP → Fe(TPPS)+ + DCQ + Cl-) in the second step. The third step is the transformation of the catalyst into a much less active form (Cat′ → Cat″) and is responsible for the unusual kinetic phenomena observed in the system.
Nonphotochemical base-catalyzed hydroxylation of 2,6-dichloroquinone by H2O2 occurs by a radical mechanism
Franzen, Stefan,Sasan, Koroush,Sturgeon, Bradley E.,Lyon, Blake J.,Battenburg, Benjamin J.,Gracz, Hanna,Dumariah, Rania,Ghiladi, Reza
, p. 1666 - 1676 (2012)
Kinetic and structural studies have shown that peroxidases are capable of the oxidation of 2,4,6-trichlorophenol (2,4,6-TCP) to 2,6-dichloro-1,4- benzoquinone (2,6-DCQ). Further reactions of 2,6-DCQ in the presence of H 2O2 and OH- yield 2,6-dichloro-3-hydroxy-1,4- benzoquinone (2,6-DCQOH). The reactions of 2,6-DCQ have been monitored spectroscopically [UV-visible and electron spin resonance (ESR)] and chromatographically. The hydroxylation product, 2,6-DCQOH, has been observed by UV-visible and characterized structurally by 1H and 13C NMR spectroscopy. The results are consistent with a nonphotochemical base-catalyzed oxidation of 2,6-DCQ at pH > 7. Because H2O 2 is present in peroxidase reaction mixtures, there is also a potential role for the hydrogen peroxide anion (HOO-). However, in agreement with previous work, we observe that the nonphotochemical epoxidation by H2O2 at pH 2O2 at low pH). Analysis of the kinetics using an Arrhenius model permits determination of the activation energy of hydroxylation (Ea = 36 kJ/mol), which is significantly lower than the activation energy of the peroxidase-catalyzed oxidation of 2,4,6-TCP (Ea = 56 kJ/mol). However, the reaction is second order in both 2,6-DCQ and OH - so that its rate becomes significant above 25 °C due to the increased rate of formation of 2,6-DCQ that feeds the second-order process. The peroxidase used in this study is the dehaloperoxidase-hemoglobin (DHP A) from Amphitrite ornata, which is used to study the effect of a catalyst on the reactions. The control experiments and precedents in studies of other peroxidases lead to the conclusion that hydroxylation will be observed following any process that leads to the formation of the 2,6-DCQ at pH > 7, regardless of the catalyst used in the 2,4,6-TCP oxidation reaction.
Hemin associated to cetyltrimethylammonium broide micelles: A biomimetic catalyst for 2,4,6-trichlorophenol degradation
Zhang, Lihui,Gu, Cheng,Hong, Ran,Zhang, Haiping
, p. 1220 - 1226 (2015)
For the first time, an efficient, green, economical biomimetic catalyst (hemin-cetyltrimethylammonium bromide micelles) was discovered to degrade 2,4,6-trichlorophenol (TCP). The degradation experiments indicate that pH, temperature, the addition of 2-methylimidazole, and the amount of hydrogen peroxide influence the degradation process. Test of reusability revealed that CTAB micelles can protect hemin from destruction by H2O2 and that the materials can be recycled. This material can be of great use for waste-water treatment.
C. fumago chloroperoxidase is also a dehaloperoxidase: Oxidative dehalogenation of halophenols
Osborne, Robert L.,Raner, Gregory M.,Hager, Lowell P.,Dawson, John H.
, p. 1036 - 1037 (2006)
We have examined the H2O2-dependent oxidative dehalogenation of 2,4,6-trihalophenols and p-halophenols catalyzed by Caldariomyces fumago chloroperoxidase (CCPO). CCPO is significantly more robust than other peroxidases and can function under harsher reaction conditions, and so its ability to dehalogenate halophenols could lead to its use as a bioremediation catalyst for aromatic dehalogenation reactions. Optimal catalysis occurred under acidic conditions (100 mM potassium phosphate solution, pH 3.0). UV-visible absorption spectroscopy, high-performance liquid chromatography, and gas chromatography/mass spectrometry clearly identified the oxidized reaction product for CCPO-catalyzed dehalogenation of 2,4,6-trihalophenols as the corresponding 2,6-dihalo-1,4-benzoquinones. This reaction has previously been reported for two His-ligated heme-containing peroxidases (see Osborne, R. L.; Taylor, L. O.; Han, K. P.; Ely, B.; Dawson, J. H. Biochem. Biophys. Res. Commun. 2004, 324, 1194-1198), but this is the first example of a Cys-ligated heme-containing peroxidase functioning as a dehaloperoxidase. The relative catalytic efficiency (turnover number) of CCPO reported herein is comparable to that of horseradish peroxidase (Ferrari, R. P.; Laurenti, E.; Trotta, F. J. Biol. Inorg. Chem. 1965, 4, 232-237). The mechanism of dehalogenation has been probed using p-halophenols as substrates. Here the major product is a dimer with 1,4-benzoquinone as the minor product. An electron-transfer mechanism is proposed that accounts for the products formed from both the 2,4,6-trihalo- and p-halophenols. Finally, we note that this is the first case of a peroxidase known primarily for its halogenation ability being shown to also dehalogenate substrates. Copyright
Single turnover studies of oxidative halophenol dehalogenation by horseradish peroxidase reveal a mechanism involving two consecutive one electron steps: Toward a functional halophenol bioremediation catalyst
Sumithran, Suganya,Sono, Masanori,Raner, Gregory M.,Dawson, John H.
, p. 316 - 321 (2012)
Horseradish peroxidase (HRP) catalyzes the oxidative para-dechlorination of the environmental pollutant/carcinogen 2,4,6-trichlorophenol (2,4,6-TCP). A possible mechanism for this reaction is a direct oxygen atom transfer from HRP compound I (HRP I) to trichlorophenol to generate 2,6-dichloro 1,4-benzoquinone, a two-electron transfer process. An alternative mechanism involves two consecutive one-electron transfer steps in which HRP I is reduced to compound II (HRP II) and then to the ferric enzyme as first proposed by Wiese et al. [F.W. Wiese, H.C. Chang, R.V. Lloyd, J.P. Freeman, V.M. Samokyszyn, Arch. Environ. Contam. Toxicol. 34 (1998) 217-222]. To probe the mechanism of oxidative halophenol dehalogenation, the reactions between 2,4,6-TCP and HRP compounds I or II have been investigated under single turnover conditions (i.e., without excess H2O2) using rapid scan stopped-flow spectroscopy. Addition of 2,4,6-TCP to HRP I leads rapidly to HRP II and then more slowly to the ferric resting state, consistent with a mechanism involving two consecutive one-electron oxidations of the substrate via a phenoxy radical intermediate. HRP II can also directly dechlorinate 2,4,6-TCP as judged by rapid scan stopped-flow and mass spectrometry. This observation is particularly significant since HRP II can only carry out one-electron oxidations. A more detailed understanding of the mechanism of oxidative halophenol dehalogenation will facilitate the use of HRP as a halophenol bioremediation catalyst.
Determination of separate inhibitor and substrate binding sites in the dehaloperoxidase-hemoglobin from Amphitrite ornata
Davis, Michael F.,Bobay, Benjamin G.,Franzen, Stefan
, p. 1199 - 1206 (2010)
Dehaloperoxidase-hemoglobin (DHP A) is a dual function protein found in the terrebellid polychaete Amphitrite ornata. A. ornata is an annelid, which inhabits estuary mudflats with other polychaetes that secrete a range of toxic brominated phenols. DHPA is capable of binding and oxidatively dehalogenating some of these compounds. DHP A possesses the ability to bind halophenols in a distinct, internal distal binding pocket. Since its discovery, the distal binding pocket has been reported as the sole binding location for halophenols; however, data herein suggest a distinction between inhibitor (monohalogenated phenol) and substrate (trihalogenated phenol) binding locations. Backbone 13Cα, 13Cβ, carbonyl 13C, amide 1H, and amide 15N resonance assignments have been made, and various halophenols were titrated into the protein. 1H- 15N HSQC experiments were collected at stoichiometric intervals during each titration, and binding locations specific for mono- and trihalogenated phenols have been identified. Titration of monohalogenated phenol induced primary changes around the distal binding pocket, while introduction of trihalogenated phenols created alterations of the distal histidine and the local area surrounding W120, a structural region that corresponds to a possible dimer interface region recently observed in X-ray crystal structures of DHP A. 2010 American Chemical Society.
Revisiting the peroxidase oxidation of 2,4,6-trihalophenols: ESR detection of radical intermediates
Sturgeon, Bradley E.,Battenburg, Benjamin J.,Lyon, Blake J.,Franzen, Stefan
, p. 1862 - 1868 (2011)
The peroxidase oxidation of 2,4,6-trichlorophenol (TCP) has been clearly shown to result in 2,6-dichloro-1,4-benzoquinone (DCQ). DCQ is a 2-electron oxidation product of TCP that has undergone para dechlorination. Many peroxidases show similar oxidation of the substrate, TCP, to yield the quinone, DCQ. Depending on the substrate, peroxidases are thought to carry out both 1- and 2-electron oxidations; the mechanism can be confirmed by the detection of both enzyme and substrate intermediates. This article presents ESR evidence for the transient 2,4,6-trichlorophenoxyl radical intermediate (TCP?), which exists free in solution, i.e., is not enzyme associated. These data are best explained as a 1-electron peroxidase oxidation of TCP to form TCP?, followed by enzyme-independent radical reactions leading to the 2-electron oxidized product. Also presented are data for the peroxidase oxidation of 2,4,6-trifluorophenol and 2,6-dichloro-4-fluorophenol.
Photophysical and photocatalytic properties of β-sulfonatoporphycenes
Baba, Tatsushi,Shimakoshi, Hisashi,Endo, Ayataka,Adachi, Chihaya,Hisaeda, Yoshio
, p. 264 - 265 (2008)
The photophysical properties and photooxidation ability of the β-sulfonatoporphycenes are reported. The photophysical parameters depend on the number of substitutions. The disulfonated porphycene 2 is expected to be a new photosensitizer due to its high catalytic activity and photostability. Copyright
Photochemical transformations of 2, 6-dichlorophenol and 2-chlorophenol with superoxide ions in the atmospheric aqueous phase
Dong, Linchang,Hu, Shuheng,Lu, Jun,Peng, Shuchuan,Zhu, Chengzhu,Zhu, Mengyu
, (2022/04/03)
The possible photochemical transformation pathways of chlorophenols (2, 6-dichlorophenol and 2-chlorophenol) with superoxide anion radical (O2·?) were studied by steady-state irradiation and 355 nm laser flash photolysis technique. O
