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Dehalogenation

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https://www.readbyqxmd.com/read/28727446/reductive-outer-sphere-single-electron-transfer-is-an-exception-rather-than-the-rule-in-natural-and-engineered-chlorinated-ethene-dehalogenation
#1
Benjamin Heckel, Stefan Cretnik, Sarah Kliegman, Orfan Shouakar-Stash, Kristopher McNeill, Martin Elsner
Chlorinated ethenes (CEs) such as perchloroethylene, trichloroethylene and dichloroethylene are notorious groundwater contaminants. Although reductive dehalogenation is key to their environmental and engineered degradation, underlying reaction mechanisms remain elusive. Outer-sphere reductive single electron transfer (OS-SET) has been proposed for such different processes as Vitamin B12-dependent biodegradation and zero-valent metal-mediated dehalogenation. Compound-specific isotope effect (13C/12C, 37Cl/35Cl) analysis offers a new opportunity to test these hypotheses...
July 20, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28716488/simultaneous-anaerobic-transformation-of-carbon-tetrachloride-to-carbon-dioxide-and-tetrachloroethene-to-ethene-in-a-continuous-flow-column
#2
Mohammad F Azizian, Lewis Semprini
The simultaneous anaerobic transformation of tetrachloroethene (PCE) and carbon tetrachloride (CT) was evaluated in a continuous flow column. The column was packed with quartz sand and bioaugmented with the Evanite culture (EV) that is capable of transforming PCE to ethene. Azizian and Semprini (2016) reported that PCE and CT could be simultaneously transformed in the column, with PCE (0.1mM) transformed mainly to ethene and CT (0.015mM) to chloroform (CF) (20%) and an unknown transformation product, likely carbon dioxide (CO2)...
July 6, 2017: Journal of Contaminant Hydrology
https://www.readbyqxmd.com/read/28715737/static-and-continuous-flow-through-pulsed-light-technology-for-pesticide-abatement-in-water
#3
Ana Beatriz Baranda, Amaia Lasagabaster, Iñigo Martínez de Marañón
Perspectives concerning pulsed light (PL) technology as a novel water decontamination treatment are overviewed in this work. Degradation of atrazine, malathion, chlorpyriphos-methyl and bromopropylate in aqueous solutions at different concentrations was performed employing static and continuous flow-through PL units. Results for both PL systems were compared in terms of efficacy of pesticides degradation and derived photoproducts formed. The pesticides degradation increased with the applied total fluence for both PL systems...
July 8, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28690604/phenol-is-the-initial-product-formed-during-growth-and-degradation-of-bromobenzene-by-tropical-marine-yeast-yarrowia-lipolytica-ncim-3589-via-an-early-dehalogenation-step
#4
Aakanksha A Vatsal, Smita S Zinjarde, Ameeta RaviKumar
Bromobenzene (BrB), a hydrophobic, recalcitrant organic compound, is listed by the environmental protection agencies as an environmental and marine pollutant having hepatotoxic, mutagenic, teratogenic, and carcinogenic effects. The tropical marine yeast Yarrowia lipolytica 3589 was seen to grow aerobically on BrB and displayed a maximum growth rate (μmax) of 0.04 h(-1). Furthermore, we also observed an increase in cell size and sedimentation velocity for the cells grown on BrB as compared to the glucose grown cells...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28689132/new-insights-into-the-spatial-variability-of-biofilm-communities-and-potentially-negative-bacterial-groups-in-hydraulic-concrete-structures
#5
Wei Cai, Yi Li, Lihua Niu, Wenlong Zhang, Chao Wang, Peifang Wang, Fangang Meng
The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35...
June 22, 2017: Water Research
https://www.readbyqxmd.com/read/28688846/evaluation-of-nitrate-effects-in-the-aqueous-photodegradability-of-selected-phenolic-pollutants
#6
G Castro, I Rodríguez, M Ramil, R Cela
The effect of nitrate in the aqueous photodegradation of five phenolic environmental pollutants (ortho-phenylphenol, OPP; methyl paraben, MeP; propyl paraben, PrP; Triclosan, TCS and bisphenol A, BPA) is evaluated. Time-course of precursor compounds and formation of transformation products (TPs) were investigated by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). Nitrate showed a positive effect in the removal of selected pollutants. Observed TPs resulted from hydroxylation, aromatic nitration (with or without molecule cleavage) and nitro dehalogenation processes...
July 3, 2017: Chemosphere
https://www.readbyqxmd.com/read/28686268/smi2-mediated-reductive-cyclization-of-%C3%AE-arylthio-ketones-a-facile-and-diastereoselective-synthesis-of-thiochroman-derivatives
#7
Hui Mao, Bing-Xin You, Lie-Jin Zhou, Ting-Ting Xie, Yi-Hang Wen, Xin Lv, Xiao-Xia Wang
SmI2-mediated reductive cyclization of β-arylthio ketones to generate thiochroman derivatives is not a generally observed process and the reported examples are limited to geminal disubstitution in the substrates. The results of the current study show that the cyclization also occurs when other substitution patterns are present, affording a general approach to dihydrothiochroman-ols in good yields and high degrees of diastereoselectivity. Besides, the halogen substitution on β-aryl is tolerated in most cases here although reductive dehalogenation has been reported to predominate in the reductive cyclization process...
July 7, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28671181/cobamide-mediated-enzymatic-reductive-dehalogenation-via-long-range-electron-transfer
#8
Cindy Kunze, Martin Bommer, Wilfred R Hagen, Marie Uksa, Holger Dobbek, Torsten Schubert, Gabriele Diekert
The capacity of metal-containing porphyrinoids to mediate reductive dehalogenation is implemented in cobamide-containing reductive dehalogenases (RDases), which serve as terminal reductases in organohalide-respiring microbes. RDases allow for the exploitation of halogenated compounds as electron acceptors. Their reaction mechanism is under debate. Here we report on substrate-enzyme interactions in a tetrachloroethene RDase (PceA) that also converts aryl halides. The shape of PceA's highly apolar active site directs binding of bromophenols at some distance from the cobalt and with the hydroxyl substituent towards the metal...
July 3, 2017: Nature Communications
https://www.readbyqxmd.com/read/28654328/biochemistry-of-catabolic-reductive-dehalogenation
#9
REVIEW
Maeva Fincker, Alfred M Spormann
A wide range of phylogenetically diverse microorganisms couple the reductive dehalogenation of organohalides to energy conservation. Key enzymes of such anaerobic catabolic pathways are corrinoid and Fe-S cluster-containing, membrane-associated reductive dehalogenases. These enzymes catalyze the reductive elimination of a halide and constitute the terminal reductases of a short electron transfer chain. Enzymatic and physiological studies revealed the existence of quinone-dependent and quinone-independent reductive dehalogenases that are distinguishable at the amino acid sequence level, implying different modes of energy conservation in the respective microorganisms...
June 20, 2017: Annual Review of Biochemistry
https://www.readbyqxmd.com/read/28649683/surface-assisted-ullmann-coupling
#10
M Lackinger
Surface-assisted Ullmann coupling is the workhorse of on-surfaces synthesis. Among the various couplings that were successfully transferred from solution to solid surfaces, Ullmann coupling is arguably the most reliable, controllable, and widespread coupling reaction. The basic reaction scheme is straightforward: halogenated precursors are deposited onto solid surfaces, normally of coinage metals. In the adsorbed state the halogen substitutents are split off by virtue of the surface's reactivity, thereby generating acitvated species that subsequently recombine by forming C-C bonds...
June 26, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28648395/the-complete-genome-of-the-tetrachloroethene-respiring-epsilonproteobacterium-sulfurospirillum-halorespirans
#11
Tobias Goris, Benjamin Schenz, Johannes Zimmermann, Mikael Lemos, Jörg Hackermüller, Torsten Schubert, Gabriele Diekert
Sulfurospirillum halorespirans is a bacterium that couples the reductive dehalogenation of chlorinated ethenes to growth. This process is called organohalide respiration (OHR), which can be of importance for bioremediation. Here, we report the complete genome of S. halorespirans, the second one of an organohalide-respiring Epsilonproteobacterium after that of Sulfurospirillum multivorans. With both genomes at hand, we were able to ascertain that the genomic region encoding OHR proteins in Epsilonproteobacteria differs from that found in organohalide-respiring bacteria (OHRB) affiliated to other phyla and that the production of a unique cobamide, norpseudo-B12, might not be limited to the model organism S...
June 22, 2017: Journal of Biotechnology
https://www.readbyqxmd.com/read/28639018/test-of-aerobic-tce-degradation-by-willows-salix-viminalis-and-willows-inoculated-with-tce-cometabolizing-strains-of-burkholderia-cepacia
#12
Lauge Peter Westergaard Clausen, Mette Martina Broholm, Ulrich Gosewinkel, Stefan Trapp
Trichloroethylene (TCE) is a widespread soil and groundwater pollutant and clean-up is often problematic and expensive. Phytoremediation may be a cost-effective solution at some sites. This study investigates TCE degradation by willows (S. viminalis) and willows inoculated with three strains of B. cepacia (301C, PR1-31 and VM1330-pTOM), using chloride formation as an indicator of dehalogenation. Willows were grown in non-sterile, hydroponic conditions for 3 weeks in chloride-free nutrient solution spiked with TCE...
June 21, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28618195/novel-reductive-dehalogenases-from-the-marine-sponge-associated-bacterium-desulfoluna-spongiiphila
#13
Jie Liu, Nora Lopez, Young-Beom Ahn, Tatyana Goldberg, Yana Bromberg, Lee J Kerkhof, Max M Häggblom
Desulfoluna spongiiphila strain AA1 is an organohalide respiring bacterium, isolated from the marine sponge Aplysina aerophoba, that can use brominated and iodinated phenols, in addition to sulfate and thiosulfate as terminal electron acceptors. The genome of Desulfoluna spongiiphila strain AA1 is approximately 6.5 Mb. Three putative reductive dehalogenase (rdhA) genes involved in respiratory metabolism of organohalides were identified within the sequence. Conserved motifs found in respiratory reductive dehalogenases (a twin arginine translocation signal sequence and two iron-sulfur clusters) were present in all three putative AA1 rdhA genes...
June 15, 2017: Environmental Microbiology Reports
https://www.readbyqxmd.com/read/28587829/pegylation-with-the-thiosuccinimido-butylamine-linker-significantly-increases-the-stability-of-haloalkane-dehalogenase-dhaa
#14
Yuan-Zhong Zhao, Wei-Li Yu, He Zheng, Xuan Guo, Nan Guo, Tao Hu, Jin-Yi Zhong
Haloalkane dehalogenase (HLD) can catalyze the hydrolytic dehalogenation of halogenated compounds. However, HLD suffers from the poor stability to resist the environmental stress. PEGylation is an effective approach to enhance the stability of enzymes. The linker is an important stabilization factor of PEGylation. Thus, the linkers of the PEGylated HLD were optimized to improve the stability of HLD in the present study. The PEGylated haloalkane dehalogenase DhaAs with methylamine (Ml), carbamate (Cm) and thiosuccinimido butylamine (Tb) linkers were prepared, respectively...
June 3, 2017: Journal of Biotechnology
https://www.readbyqxmd.com/read/28566709/targeted-radionuclide-therapy-with-astatine-211-oxidative-dehalogenation-of-astatobenzoate-conjugates
#15
David Teze, Dumitru-Claudiu Sergentu, Valentina Kalichuk, Jacques Barbet, David Deniaud, Nicolas Galland, Rémi Maurice, Gilles Montavon
(211)At is a most promising radionuclide for targeted alpha therapy. However, its limited availability and poorly known basic chemistry hamper its use. Based on the analogy with iodine, labelling is performed via astatobenzoate conjugates, but in vivo deastatination occurs, particularly when the conjugates are internalized in cells. Actually, the chemical or biological mechanism responsible for deastatination is unknown. In this work, we show that the C-At "organometalloid" bond can be cleaved by oxidative dehalogenation induced by oxidants such as permanganates, peroxides or hydroxyl radicals...
May 31, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28553478/nature-s-hydrides-rapid-reduction-of-halocarbons-by-folate-model-compounds
#16
Michael K Denk, Nicholas S Milutinović, Katherine M Marczenko, Natalie M Sadowski, Athanasios Paschos
Halocarbons R-X are reduced to hydrocarbons R-H by folate model compounds under biomimetic conditions. The reactions correspond to a halide-hydride exchange with the methylenetetrahydrofolate (MTHF) models acting as hydride donors. The MTHF models are also functional equivalents of dehalohydrogenases but, unlike these enzymes, do not require a metal cofactor. The reactions suggest that halocarbons have the potential to act as endocrinological disruptors of biochemical pathways involving MTHF. As a case in point, we observe the rapid reaction of the MTHF models with the inhalation anaesthetic halothane...
March 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28530808/%C3%AE-halo-amides-as-competent-latent-enolates-direct-catalytic-asymmetric-mannich-type-reaction
#17
Bo Sun, Pandur Venkatesan Balaji, Naoya Kumagai, Masakatsu Shibasaki
α-Halogenated carbonyl compounds are susceptible to dehalogenation and thus largely neglected as enolate precursors in catalytic enantioselective C-C bond-forming reactions. By merging the increased stability of the α-C-halogen bond of amides and the direct enolization methodology of the designed amide, we explored a direct catalytic asymmetric Mannich-type reaction of α-halo 7-azaindoline amides with N-carbamoyl imines. All α-halo substituents, α-F, -Cl, -Br, -I amides, were tolerated to provide the Mannich-adducts in a highly stereoselective manner without undesirable dehalogenation...
June 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28521164/biotransformation-of-hexabromocyclododecanes-with-hexachlorocyclohexane-transforming-sphingobium-chinhatense-strain-ip26
#18
Norbert V Heeb, Andreas Grubelnik, Birgit Geueke, Hans-Peter E Kohler, Peter Lienemann
Bacterial evolution has resulted in the appearance of several Sphingomonadacea strains that gained the ability to metabolize hexachlorocyclohexanes (HCHs). HCHs have been widely used as pesticides but were banned under the Stockholm Convention on persistent organic pollutants (POPs) in 2009. Here we present evidence for bacterial transformation reactions of hexabromocyclododecanes (HBCDs), which are structurally related to HCHs. HBCDs were used as flame retardants. They are now also considered as POPs and their production and use is restricted since 2013...
May 11, 2017: Chemosphere
https://www.readbyqxmd.com/read/28499743/resolution-of-the-uncertainty-in-the-kinetic-mechanism-for-the-trans-3-chloroacrylic-acid-dehalogenase-catalyzed-reaction
#19
Jamison P Huddleston, Susan C Wang, Kenneth A Johnson, Christian P Whitman
trans- and cis-3-Chloroacrylic acid dehalogenase (CaaD and cis-CaaD, respectively) catalyze the hydrolytic dehalogenation of their respective isomers and represent key steps in the bacterial conversion of 1,3-dichloropropene to acetaldehyde. In prior work, a kinetic mechanism for the CaaD-catalyzed reaction could not be unequivocally determined because (1) the order of product release could not be determined and (2) the fluorescence factor for the enzyme species, E*PQ (where P = bromide and Q = malonate semialdehyde, the two products of the reaction) could not be assigned...
June 1, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28463483/a-field-trial-of-tce-phytoremediation-by-genetically-modified-poplars-expressing-cytochrome-p450-2e1
#20
Emily K Legault, C Andrew James, Keith Stewart, Indulis Muiznieks, Sharon L Doty, Stuart E Strand
A controlled field study was performed to evaluate the effectiveness of transgenic poplars for phytoremediation. Three hydraulically contained test beds were planted with 12 transgenic poplars, 12 wild type (WT) poplars, or left unplanted, and dosed with equivalent concentrations of trichloroethylene (TCE). Removal of TCE was enhanced in the transgenic tree bed, but not to the extent of the enhanced removal observed in laboratory studies. Total chlorinated ethene removal was 87% in the CYP2E1 bed, 85% in the WT bed, and 34% in the unplanted bed in 2012...
June 6, 2017: Environmental Science & Technology
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