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Dehalogenation

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https://www.readbyqxmd.com/read/29040474/co-occurrence-of-genes-for-aerobic-and-anaerobic-biodegradation-of-dichloroethane-in-organochlorine-contaminated-groundwater
#1
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 (qPCR) 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...
October 12, 2017: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29028295/generation-and-characterization-of-a-meta-aryne-on-cu-and-nacl-surfaces
#2
Niko Pavliček, Zsolt Majzik, Sara Collazos, Gerhard Meyer, Dolores Pérez, Enrique Guitian, 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 AFM 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 13, 2017: ACS Nano
https://www.readbyqxmd.com/read/28989606/rapid-access-to-substituted-2-naphthyne-intermediates-via-the-benzannulation-of-halogenated-silylalkynes
#3
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
#4
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
#5
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
#6
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
#7
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
#8
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
#9
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
#10
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
#11
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
https://www.readbyqxmd.com/read/28870506/pcb-in-the-environment-bio-based-processes-for-soil-decontamination-and-management-of-waste-from-the-industrial-production-of-pleurotus-ostreatus
#12
Giovanna Siracusa, Simone Becarelli, Roberto Lorenzi, Alessandro Gentini, Simona Di Gregorio
Polychlorinated biphenyls (PCBs) are hazardous soil contaminants for which a bio-based technology for their recovery is essential. The objective of this study was to validate the exploitation of spent mushroom substrate (SMS), a low or null cost organic waste derived from the industrial production of P. ostreatus, as bulking agent in a dynamic biopile pilot plant. The SMS shows potential oxidative capacity towards recalcitrant compounds. The aim was consistent with the design of a process of oxidation of highly chlorinated PCBs, which is independent from their reductive dehalogenation...
October 25, 2017: New Biotechnology
https://www.readbyqxmd.com/read/28869789/subtle-changes-in-the-active-site-architecture-untangled-overlapping-substrate-ranges-and-mechanistic-differences-of-two-reductive-dehalogenases
#13
Cindy Kunze, Gabriele Diekert, Torsten Schubert
Reductive dehalogenases (RDases) of organohalide-respiring bacteria are cobamide-containing iron-sulfur proteins that catalyze different reductive dehalogenation reactions. Here, we report a functional analysis of two recombinant RDases, the tetrachloroethene (PCE) reductive dehalogenase (PceA) of Desulfitobacterium hafniense Y51 and the 1,2-dichloroethane (1,2-DCA) reductive dehalogenase (DcaA) of Desulfitobacterium dichloroeliminans DCA1. Both enzymes share 88% protein sequence identity, but appeared to have divergent mechanisms...
September 4, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28859807/construction-and-functional-analysis-of-a-whole-cell-biocatalyst-based-on-cyp108n7
#14
Chao Guo, Zhong-Liu Wu
Cytochrome P450 enzymes are versatile biocatalysts with great potential in biotechnology. A new bacterial P450 was identified from the genome of Rhodococcus wratislaviensis NBRC 100605 and annotated as CYP108N7. The enzyme accepted the ferredoxin and ferredoxin reductase from spinach as surrogate redox partners for improved electron transfer efficiency. It was heterologous expressed in Escherichia coli together with the redox partners and a glucose dehydrogenase which supplied the reduced cofactor NADPH. The resulting whole-cell biocatalyst catalyzed a variety of reactions including sulfoxidation, epoxidation, hydroxylation, demethylation and dehalogenation...
November 2017: Enzyme and Microbial Technology
https://www.readbyqxmd.com/read/28829078/dissimilar-catalytic-behavior-of-molecular-or-colloidal-palladium-systems-with-a-new-nhc-ligand
#15
Fernando Gómez-Villarraga, Jonathan De Tovar, Miguel Guerrero, Pau Nolis, Teodor Parella, Pierre Lecante, Nuria Romero, Lluís Escriche, Roger Bofill, Josep Ros, Xavier Sala, Karine Philippot, Jordi García-Antón
In this work, we describe the synthesis of a new N-heterocyclic carbene (NHC) ligand, derived from a hybrid pyrazole-imidazolium scaffold, namely 1-[2-(3,5-dimethylpyrazol-1-yl)ethyl]-3-((S)-1-phenylethyl)-3H-imidazol-2-ylidene (L). This ligand has been used as a stabilizer for the organometallic synthesis of palladium(0) nanoparticles (Pd NPs). L presents a better stabilizing effect than its pre-carbenic HLCl counterpart, allowing the formation of isolated Pd NPs while HLCl yields aggregated ones. Additionally, molecular Pd(ii) coordination compounds of L and HLCl were synthesized and characterized to better understand the coordination modes of these ligands...
September 12, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28811148/metagenomes-from-deep-baltic-sea-sediments-reveal-how-past-and-present-environmental-conditions-determine-microbial-community-composition
#16
Ian P G Marshall, Søren M Karst, Per H Nielsen, Bo Barker Jørgensen
Microbial communities that lived near the sediment surface in the past become slowly buried and are the source of deep subsurface communities thousands of years later. We used metagenomes to analyse how the composition of buried microbial communities may change to conform to altered environmental conditions at depth. Sediment samples were collected from down to 85m below sea floor during the Integrated Ocean Drilling Program Expedition 347, "Baltic Sea Paleoenvironment". The sediments vary in age, organic carbon content, porewater salinity, and other parameters that reflect the changing Baltic environment from the last ice age and throughout the Holocene...
August 12, 2017: Marine Genomics
https://www.readbyqxmd.com/read/28810730/hydrogen-isotope-fractionation-during-the-biodegradation-of-1-2-dichloroethane-potential-for-pathway-identification-using-a-multi-element-c-cl-and-h-isotope-approach
#17
Jordi Palau, Orfan Shouakar-Stash, Siti Hatijah Mortan, Rong Yu, Monica Rosell, Ernest Marco-Urrea, David L Freedman, Ramon Aravena, Albert Soler, Daniel Hunkeler
Even though multi-element isotope fractionation patterns provide crucial information with which to identify contaminant degradation pathways in the field, those involving hydrogen are still lacking for many halogenated groundwater contaminants and degradation pathways. This study investigates for the first time hydrogen isotope fractionation during both aerobic and anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) using five microbial cultures. Transformation-associated isotope fractionation values (εbulk(H)) were -115 ± 18‰ (aerobic C-H bond oxidation), -34 ± 4‰ and -38 ± 4‰ (aerobic C-Cl bond cleavage via hydrolytic dehalogenation), and -57 ± 3‰ and -77 ± 9‰ (anaerobic C-Cl bond cleavage via reductive dihaloelimination)...
September 1, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28809549/mesocosm-studies-on-the-efficacy-of-bioamended-activated-carbon-for-treating-pcb-impacted-sediment
#18
Rayford B Payne, Upal Ghosh, Harold D May, Christopher W Marshall, Kevin R Sowers
This report describes results of a bench-scale treatability study to evaluate the efficacy of bioaugmentation with bioamended activated carbon (AC) for in situ treatment of polychlorinated biphenyl (PCB) impacted sediments. To this end, the ability of PCB transforming microorganisms to degrade and reduce the overall concentration of PCBs in sediment was determined in 2 L recirculating mesocosms designed to simulate conditions in Abraham's Creek in Quantico, Virginia. Ten sediment mesocosms were tested for the effects of AC alone, AC with slow release electron donor (cellulose) and different concentrations and combinations of PCB dehalogenating and degrading microorganisms added as bioamendments...
August 30, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28805056/polymer-dehalogenation-enabled-fast-fabrication-of-n-s-codoped-carbon-materials-for-superior-supercapacitor-and-deionization-applications
#19
Yingna Chang, Guoxin Zhang, Biao Han, Haoyuan Li, Cejun Hu, Yingchun Pang, Zheng Chang, Xiaoming Sun
Doped carbon materials (DCM) with multiple heteroatoms hold broad interest in electrochemical catalysis and energy storage but require several steps to fabricate, which greatly hinder their practical applications. In this study, a facile strategy is developed to enable the fast fabrication of multiply doped carbon materials via room-temperature dehalogenation of polyvinyl dichloride (PVDC) promoted by KOH with the presence of different organic dopants. A N,S-codoped carbon material (NS-DCM) is demonstratively synthesized using two dopants (dimethylformamide for N doping and dimethyl sulfoxide for S doping)...
August 24, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28780870/enantioselective-hydrogen-atom-transfer-discovery-of-catalytic-promiscuity-in-flavin-dependent-ene-reductases
#20
Braddock A Sandoval, Andrew J Meichan, Todd K Hyster
Flavin has long been known to function as a single electron reductant in biological settings, but this reactivity has rarely been observed with flavoproteins used in organic synthesis. Here we describe the discovery of an enantioselective radical dehalogenation pathway for α-bromoesters using flavin-dependent 'ene'-reductases. Mechanistic experiments support the role of flavin hydroquinone as a single electron reductant, flavin semiquinone as the hydrogen atom source, and the enzyme as the source of chirality...
August 11, 2017: Journal of the American Chemical Society
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