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Dehalogenation

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https://www.readbyqxmd.com/read/29228161/reductive-tetrachloroethene-dehalogenation-in-the-presence-of-oxygen-by-sulfurospirillum-multivorans-physiological-studies-and-proteome-analysis
#1
Jennifer Gadkari, Tobias Goris, Christian L Schiffmann, Raffael Rubick, Lorenz Adrian, Torsten Schubert, Gabriele Diekert
Reductive dehalogenation of organohalides is carried out by organohalide-respiring bacteria (OHRB) in anoxic environments. The tetrachloroethene (PCE)-respiring Epsilonproteobacterium Sulfurospirillum multivorans is one of few OHRB able to respire oxygen. Therefore, we investigated the organism's capacity to dehalogenate PCE in the presence of oxygen, which would broaden the applicability to use S. multivorans, unlike other commonly oxygen-sensitive OHRB, for bioremediation, e.g. at oxic/anoxic interphases...
December 5, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29211312/tris-pentafluoroethyl-stannane-tin-hydride-chemistry-with-an-electron-deficient-stannane
#2
Markus Wiesemann, Mark Niemann, Johannes Klösener, Beate Neumann, Hans-Georg Stammler, Berthold Hoge
A versatile two-step synthesis for tris(pentafluoroethyl)stannane, HSn(C2F5)3, is presented. Electron withdrawing C2F5 groups significantly influence the polarity of the tin-hydrogen bond allowing facile deprotonation of the compound even in water. The utility of this electron-deficient stannane was illustrated in hydrostannylations of alkenes and alkynes as well as in dehalogenation reactions. The remarkable, high reactivity of HSn(C2F5)3 is demonstrated in fast hydrostannylations, even in the absence of activators, whereby the regioselectivity of this process turned out to be solvent dependent...
December 6, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29177304/dehalogenation-of-vicinal-dihalo-compounds-by-1-1-bis-trimethylsilyl-1h-1-h-4-4-bipyridinylidene-for-giving-alkenes-and-alkynes-in-a-salt-free-manner
#3
Supriya Rej, Suman Pramanik, Hayato Tsurugi, Kazushi Mashima
We report a transition metal-free dehalogenation of vicinal dihalo compounds by 1,1'-bis(trimethylsilyl)-1H,1'H-4,4'-bipyridinylidene (1) under mild conditions, in which trimethylsilyl halide and 4,4'-bipyridine were generated as byproducts. The synthetic protocol for this dehalogenation reaction was effective for a wide scope of dibromo compounds as substrates while keeping the various functional groups intact. Furthermore, the reduction of vicinal dichloro alkanes and vicinal dibromo alkenes also proceeded in a salt-free manner to afford the corresponding alkenes and alkynes...
November 27, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29175406/evaluation-of-carbon-isotope-fractionation-during-anaerobic-reductive-dehalogenation-of-chlorinated-and-brominated-benzenes
#4
Seo Yean Sohn, Kevin Kuntze, Ivonne Nijenhuis, Max M Häggblom
Compound specific stable isotope analysis (CSIA) has been established as a useful tool to evaluate in situ biodegradation. Here, CSIA was used to determine microbial dehalogenation of chloro- and bromobenzenes in microcosms derived from Hackensack River sediments. Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) was used to measure carbon isotope fractionation during reductive dehalogenation of hexachlorobenzene (HCB), pentachlorobenzene (PeCB), 1,2,3,5-tetrachlorobenzene (TeCB), 1,2,3,5-tetrabromobenzene (TeBB), and 1,3,5-tribromobenzene (TriBB)...
November 20, 2017: Chemosphere
https://www.readbyqxmd.com/read/29161603/37cl-compound-specific-isotope-analysis-and-assessment-of-functional-genes-for-monitoring-monochlorobenzene-mcb-biodegradation-under-aerobic-conditions
#5
Massimo Marchesi, Luca Alberti, Orfan Shouakar-Stash, Ilaria Pietrini, Francesca de Ferra, Giovanna Carpani, Ramon Aravena, Andrea Franzetti, Tatiana Stella
A laboratory approach was adopted in this study to explore the potential of 37Cl-CSIA in combination with 13C-CSIA and Biological Molecular Tools (BMTs) to estimate the occurrence of monochloroenzene (MCB) aerobic biodegradation. A new analytical method for 37Cl-CSIA of MCB was developed in this study. This methodology using a GC-IRMS allowed to determine δ37Cl values within an internal error of ±0.3‰. Samples from a heavily MCB contaminated site were collected and MCB aerobic biodegradation microcosms with indigenous cultures in natural and enhanced conditions were set up...
November 18, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29116682/flavin-n5-covalent-intermediate-in-the-non-redox-dehalogenation-reaction-catalyzed-by-an-atypical-flavoenzyme
#6
Yumin Dai, Karina Kizjakina, Ashley C Campbell, David A Korasick, John J Tanner, Pablo Sobrado
The flavin-dependent enzyme 2-haloacrylate hydratase (2-HAH) catalyzes the conversion of 2-chloroacrylate, a major component in the manufacture of acrylic polymers, to pyruvate. The enzyme from has been expressed in Escherichia coli, purified, and characterized. 2-HAH is monomeric in solution and contains a non-covalent, yet tightly bound, FAD. Although the reaction catalyzed is redox neutral, 2-HAH is active only in the reduced state. A covalent flavin-substrate intermediate, consistent with the flavin-acrylate iminium ion, was trapped with cyanoborohydride and characterized by mass spectrometry...
November 8, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/29112726/reconstructed-genomes-of-novel-dehalococcoides-mccartyi-strains-from-1-2-3-4-tetrachlorodibenzo-p-dioxin-dechlorinating-enrichment-cultures-reveal-divergent-reductive-dehalogenase-gene-profiles
#7
Hang T Dam, John Vollmers, Anne-Kristin Kaster, Max M Häggblom
Polychlorinated dibenzo-p-dioxin (PCDD) contaminated sites are widespread and associated with a variety of anthropogenic sources. PCDDs and other organohalide pollutants can serve as terminal electron acceptors for anaerobic respiration by specialized bacteria containing reductive dehalogenases (RdhA). These microorganisms, therefore, play an important role in bioremediation of PCDD contaminated sites. Two anaerobic enrichment cultures established using sediments collected from the PCDD polluted Hackensack (USA) and Kymijoki (Finland) rivers showed robust reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TeCDD)...
November 3, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29069488/triple-element-compound-specific-stable-isotope-analysis-of-1-2-dichloroethane-for-characterization-of-the-underlying-dehalogenation-reaction-in-two-dehalococcoides-mccartyi-strains
#8
Steffi Franke, Christina Lihl, Julian Renpenning, Martin Elsner, Ivonne Nijenhuis
Chlorinated ethanes belong to the most common groundwater and soil contaminants. Of these, 1,2-dichloroethane (1,2-DCA) is an man-made, persistent and toxic contaminant, released due to improper waste treatment at versatile production sites. This study investigated the anaerobic transformation of 1,2-DCA by Dehalococcoides mccartyi strain 195 and strain BTF08 using triple-element compound-specific stable isotope analysis (CSIA) of carbon, chlorine and hydrogen for the first time. Isotope fractionation patterns for carbon (ε C BTF08   =   -28...
October 22, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29054081/reductive-dehalogenation-of-ddt-with-folate-models-formation-of-the-ddt-metabolite-spectrum-under-biomimetic-conditions
#9
Michael K Denk, Nicholas S Milutinović
The insecticide DDT is an omnipresent environmental contaminant and an ongoing toxicological concern. The recent discovery that methylenetetrahydrofolate (MTHF) models are capable of reducing a range of halocarbons to hydrocarbons under biomimetic conditions has prompted us to investigate the possible role of MTHF in the metabolism of DDT. We now report that the reaction of MTHF models with DDT produces no less than five known in vivo metabolites of DDT, namely DDD, DDE, DDMU, DBP, and DDM. The capability of the MTHF models to produce the full spectrum of known DDT dehalogenation products is strong evidence that the mechanistically obscure metabolism of DDT may involve MTHF...
October 11, 2017: Chemosphere
https://www.readbyqxmd.com/read/29040474/co-occurrence-of-genes-for-aerobic-and-anaerobic-biodegradation-of-dichloroethane-in-organochlorine-contaminated-groundwater
#10
Jacob E Munro, Önder Kimyon, Deborah J Rich, Joanna Koenig, Sihui Tang, Adrian Low, Matthew Lee, Mike Manefield, Nicholas V Coleman
1,2-Dichloroethane (DCA) is a problematic groundwater pollutant. Factors influencing the distribution and activities of DCA-degrading bacteria are not well understood, which has hampered their application for bioremediation. Here, we used quantitative PCR to investigate the distribution of putative DCA-dehalogenating bacteria at a DCA-impacted site in Sydney (Australia). The dehalogenase genes dhlA, tceA and bvcA were detected in all groundwater samples (n = 15), while vcrA was found in 11/15 samples. The 16S rRNA gene sequences specific to the dehalogenating genera Dehalobacter, Desulfitobacterium and Dehalogenimonas were detected in 15/15, 13/15 and 13/15 samples, respectively, while Dehalococcoides sequences were found in 9/15 samples...
November 1, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29028295/generation-and-characterization-of-a-meta-aryne-on-cu-and-nacl-surfaces
#11
Niko Pavliček, Zsolt Majzik, Sara Collazos, Gerhard Meyer, Dolores Pérez, Enrique Guitián, Diego Peña, Leo Gross
We describe the generation of a meta-aryne at low temperature (T = 5 K) using atomic manipulation on Cu(111) and on bilayer NaCl on Cu(111). We observe different voltage thresholds for dehalogenation of the precursor and different reaction products depending on the substrate surface. The chemical structure is resolved by atomic force microscopy with CO-terminated tips, revealing the radical positions and confirming a diradical rather than an anti-Bredt olefin structure for this meta-aryne on NaCl.
October 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28989606/rapid-access-to-substituted-2-naphthyne-intermediates-via-the-benzannulation-of-halogenated-silylalkynes
#12
Samuel J Hein, Dan Lehnherr, William R Dichtel
Aryne intermediates are versatile and important reactive intermediates for natural product and polymer synthesis. 2-Naphthynes are relatively unexplored because few methods provide precursors to these intermediates, especially for those bearing additional substituents. Here we report a general synthetic strategy to access 2-naphthyne precursors through an Asao-Yamamoto benzannulation of ortho-(phenylethynyl)benzaldehydes with halo-silylalkynes. This transformation provides 2-halo-3-silylnaphthalenes with complete regioselectivity...
August 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28987410/variable-dual-carbon-bromine-stable-isotope-fractionation-during-enzyme-catalyzed-reductive-dehalogenation-of-brominated-ethenes
#13
Angela Woods, Kevin Kuntze, Faina Gelman, Ludwik Halicz, Ivonne Nijenhuis
The potential of compound-specific stable isotope analysis (CSIA) to characterize biotransformation of brominated organic compounds (BOCs) was assessed and compared to chlorinated analogues. Sulfurospirillum multivorans and Desulfitobacterium hafniense PCE-S catalyzed the dehalogenation of tribromoethene (TBE) to either vinyl bromide (VB) or ethene, respectively. Significantly lower isotope fractionation was observed for TBE dehalogenation by S. multivorans (εC = -1.3 ± 0.2‰) compared to D. hafniense (εC = -7...
September 27, 2017: Chemosphere
https://www.readbyqxmd.com/read/28980215/photodegradative-fate-and-potential-phototoxic-products-of-bromocarbazoles-and-chlorocarbazoles-in-water
#14
John Mumbo, Dominik Deyerling, Bernhard Henkelmann, Gerd Pfister, Karl-Werner Schramm
Bromocarbazoles and chlorocarbazoles are emerging environmental contaminants that have been reported to be persistent and possessing dioxin-like toxicity; however, their photodegradative fate in water is unknown. The photodegradation of 3-bromocarbazole, 3-chlorocarbazole, and 3,6-dichlorocarbazole was determined in ultrapure water. They proceeded by direct photolysis and followed first-order kinetics. The rate constants (k) were 0.4838, 0.3454, and 0.4422 h(-1) corresponding to half-lives (t 1/2) 1.81, 2...
October 5, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28923662/selecting-of-a-cytochrome-p450cam-sesam-library-with-3-chloroindole-and-endosulfan-identification-of-mutants-that-dehalogenate-3-chloroindole
#15
Shaima Kammoonah, Brinda Prasad, Priyadarshini Balaraman, Hemanshu Mundhada, Ulrich Schwaneberg, Erika Plettner
Cytochrome P450cam (a camphor hydroxylase) from the soil bacterium Pseudomonas putida shows potential importance in environmental applications such as the degradation of chlorinated organic pollutants. Seven P450cam mutants generated from Sequence Saturation Mutagenesis (SeSaM) and isolated by selection on minimal media with either 3-chloroindole or the insecticide endosulfan were studied for their ability to oxidize of 3-chloroindole to isatin. The wild-type enzyme did not accept 3-chloroindole as a substrate...
September 18, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28919881/genomic-and-transcriptomic-analysis-of-growth-supporting-dehalogenation-of-chlorinated-methanes-in-methylobacterium
#16
Pauline Chaignaud, Bruno Maucourt, Marion Weiman, Adriana Alberti, Steffen Kolb, Stéphane Cruveiller, Stéphane Vuilleumier, Françoise Bringel
Bacterial adaptation to growth with toxic halogenated chemicals was explored in the context of methylotrophic metabolism of Methylobacterium extorquens, by comparing strains CM4 and DM4, which show robust growth with chloromethane and dichloromethane, respectively. Dehalogenation of chlorinated methanes initiates growth-supporting degradation, with intracellular release of protons and chloride ions in both cases. The core, variable and strain-specific genomes of strains CM4 and DM4 were defined by comparison with genomes of non-dechlorinating strains...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28918639/identification-of-novel-hydrogen-substituted-polyfluoroalkyl-ether-sulfonates-in-environmental-matrices-near-metal-plating-facilities
#17
Yongfeng Lin, Ting Ruan, Aifeng Liu, Guibin Jiang
Environmental occurrence and behaviors of 6:2 chlorinated polyfluoroalkyl ether sulfonate (Cl-6:2 PFESA, with trade name F-53B) have been receiving increased attention recently. Nevertheless, its potential fates under diversified conditions remain concealed. In this study, susceptibility of Cl-6:2 PFESA to reductive dehalogenation was tested in an anaerobic super-reduced cyanocobalamin assay. A rapid transformation of dosed Cl-6:2 PFESA was observed, with a hydrogen-substituted polyfluoroalkyl ether sulfonate (1H-6:2 PFESA) identified as the predominant product by a nontarget screening workflow...
October 17, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28914537/coupling-bioflocculation-of-dehalococcoides-mccartyi-to-high-rate-reductive-dehalogenation-of-chlorinated-ethenes
#18
Anca G Delgado, Devyn Fajardo-Williams, Emily Bondank, Sofia Esquivel-Elizondo, Rosa Krajmalnik-Brown
Continuous bioreactors operated at low hydraulic retention times have rarely been explored for reductive dehalogenation of chlorinated ethenes. The inability to consistently develop such bioreactors affects the way growth approaches for Dehalococcoides mccartyi bioaugmentation cultures are envisioned. It also affects interpretation of results from in situ continuous treatment processes. We report bioreactor performance and dehalogenation kinetics of a D. mccartyi-containing consortium in an upflow bioreactor...
September 15, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28911771/measurement-and-prediction-of-chlorine-kinetic-isotope-effects-in-enzymatic-systems
#19
Lukasz Szatkowski, Rabindra Nath Manna, Anna Grzybkowska, Rafał Kamiński, Agnieszka Dybala-Defratyka, Piotr Paneth
Approaches to determine chlorine kinetic isotope effects (Cl-KIEs) on enzymatic dehalogenations are discussed and illustrated by representative examples. Three aspects are considered. First methodology for experimental measurement of Cl-KIEs, with stress being on FAB-IRMS technique developed in our laboratory, is described. Subsequently, we concentrate our discussion on the consequences of reaction complexity in the interpretation of experimental values, a problem especially important in cases of polychlorinated reactants...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28881326/remediation-of-electronic-waste-polluted-soil-using-a-combination-of-persulfate-oxidation-and-chemical-washing
#20
Fu Chen, Zhanbin Luo, Gangjun Liu, Yongjun Yang, Shaoliang Zhang, Jing Ma
Laboratory experiments were conducted to investigate the efficiency of a simultaneous chemical extraction and oxidation for removing persistent organic pollutants (POPs) and toxic metals from an actual soil polluted by the recycling activity of electronic waste. Various chemicals, including hydroxypropyl-β-cyclodextrin (HPCD), citric acid (CA) and sodium persulfate (SP) were applied synchronously with Fe(2+) activated oxidation to enhance the co-removal of both types of pollutants. It is found that the addition of HPCD can enhance POPs removal through solubilization of POPs and iron chelation; while the CA-chelated Fe(2+) activation process is effective for extracting metals and degrading residual POPs...
December 15, 2017: Journal of Environmental Management
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