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Dehalogenation

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https://www.readbyqxmd.com/read/29455518/surface-adatom-mediated-structural-transformation-in-bromoarene-monolayers-precursor-phases-in-surface-ullmann-reaction
#1
Qitang Fan, Liming Liu, Jingya Dai, Tao Wang, Huanxin Ju, Jin Zhao, Julian Kuttner, Gerhard Hilt, J Michael Gottfried, Junfa Zhu
Structural transformations of supramolecular systems triggered by external stimuli maintain great potential for application in the fabrication of molecular storage devices. Using combined ultrahigh vacuum scanning tunneling microscopy (UHV-STM), X-ray photoemission spectroscopy (XPS), and density functional theory (DFT) calculation, we unambiguously observed the surface adatom mediated structural transformation from 4,4''-dibromo-m-terphenyl (DMTP)-based halogen-bonded networks to DMTP-Cu(Ag) coordination networks on Cu(111) and Ag(111) at low temperatures...
February 19, 2018: ACS Nano
https://www.readbyqxmd.com/read/29388368/covalent-immobilization-of-halohydrin-dehalogenase-for-efficient-synthesis-of-epichlorohydrin-in-an-integrated-bioreactor
#2
Shu-Ping Zou, Kai Gu, Yu-Guo Zheng
Halohydrin dehalogenase (HHDH)-mediated dehalogenation of 1,3-dichloro-2-propanol (1,3-DCP) is a key step in the chemoenzymatic synthesis of epichlorohydrin (ECH) from glycerol. In this study, a covalent immobilization strategy was employed to enhance the stability of Agrobacterium tumefaciens HHDH by using epoxy resin ES-103B as a carrier. Under optimal conditions, the activity recovery of ES-103B-immobilized HHDH (HHDH@ES-103B) was 62.4% and the specific activity was 1604 U/g. The HHDH@ES-103B exhibited excellent thermostability, with a half-life of 68...
February 1, 2018: Biotechnology Progress
https://www.readbyqxmd.com/read/29385441/anaerobic-microbial-dehalogenation-and-its-key-players-in-the-contaminated-bitterfeld-wolfen-megasite
#3
Ivonne Nijenhuis, Reiner Stollberg, Ute Lechner
The megasite Bitterfeld-Wolfen is highly contaminated as result of accidents and because of dumping of wastes from local chemical industries in the last century. A variety of contaminants including chlorinated ethenes and benzenes, hexachlorohexanes and chlorinated dioxins can still be found in the groundwater and (river) sediments. Investigations of the in situ microbial transformation of organohalides have been performed only over the last two decades at this megasite. In this review, we summarize the research on the activity of anaerobic dehalogenating bacteria at the field site in Bitterfeld-Wolfen, focusing on chlorinated ethenes, monochlorobenzene and chlorinated dioxins...
January 29, 2018: FEMS Microbiology Ecology
https://www.readbyqxmd.com/read/29380873/annotation-of-gut-bacterial-taxonomic-and-functional-diversity-in-spodoptera-litura-and-spilosoma-obliqua
#4
Kiran G Bapatla, Arjun Singh, Srujana Yeddula, Ramanagouda H Patil
The insect gut has been the house of many taxonomically and physiologically diverse groups of microbial colonizers as symbionts and commensals, which are evolving to support the physiological requirement of insects. Lepidoptera is one of the important family of class hexapoda, comprising agriculture insect pest Spodoptera litura and Spilosoma obliqua. Information on gut microbiota and their functional role in these insects was meager to elucidate the wide-ranging survivalist mechanisms. In this context, we analyzed the composition, diversity and functional role of gut bacteria in S...
January 30, 2018: Journal of Basic Microbiology
https://www.readbyqxmd.com/read/29363941/heterologous-production-and-purification-of-a-functional-chloroform-reductive-dehalogenase
#5
Bat-Erdene Jugder, Karl A P Payne, Karl Fisher, Susanne Bohl, Helene Lebhar, Mike Manefield, Matthew Lee, David Leys, Christopher P Marquis
Reductive dehalogenases (RDase) are key enzymes involved in the respiratory process of anaerobic organohalide respiring bacteria (ORB). Heterologous expression of respiratory RDases is desirable for structural and functional studies, however there are few reports of successful expression of these enzymes. Dehalobacter sp. strain UNSWDHB is an ORB, whose preferred electron acceptor is chloroform. This study describes efforts to express recombinant reductive dehalogenase (TmrA), derived from UNSWDHB, using the heterologous hosts Escherichia coli and Bacillus megaterium...
January 24, 2018: ACS Chemical Biology
https://www.readbyqxmd.com/read/29362453/insights-into-the-molecular-mechanism-of-dehalogenation-catalyzed-by-d-2-haloacid-dehalogenase-from-crystal-structures
#6
Yayue Wang, Yanbin Feng, Xupeng Cao, Yinghui Liu, Song Xue
D-2-haloacid dehalogenases (D-DEXs) catalyse the hydrolytic dehalogenation of D-2-haloacids, releasing halide ions and producing the corresponding 2-hydroxyacids. A structure-guided elucidation of the catalytic mechanism of this dehalogenation reaction has not been reported yet. Here, we report the catalytic mechanism of a D-DEX, HadD AJ1 from Pseudomonas putida AJ1/23, which was elucidated by X-ray crystallographic analysis and the H218O incorporation experiment. HadD AJ1 is an α-helical hydrolase that forms a homotetramer with its monomer including two structurally axisymmetric repeats...
January 23, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29344709/microbial-characterization-of-methanogenic-and-iron-reducing-consortium-in-reactors-with-polychlorinated-biphenyls
#7
Mara R de Lima E Silva, Regiane C Correa, Isabel K Sakamoto, Maria B A Varesche
Recent papers have confirmed current environmental pollution and the continuous release of polychlorinated biphenyls (PCBs) despite the prohibition of its manufacture worldwide. As the dehalogenating microorganisms are able to remove halogens from various analogous compounds, the characterization of PCB metabolisms can improve the degradation of similar compounds. Thus, this study extensively evaluated the microbial community developed in methanogenic and iron-reducing reactors. The horizontal-flow anaerobic reactor (HAIB) with real waste of Aroclor (1 mL L-1) was fed with mineral medium, ethanol, and sodium formate...
January 17, 2018: Current Microbiology
https://www.readbyqxmd.com/read/29322098/diuron-degradation-by-bacteria-from-soil-of-sugarcane-crops
#8
Tassia C Egea, Roberto da Silva, Maurício Boscolo, Janaina Rigonato, Diego A Monteiro, Danilo Grünig, Humberto da Silva, Frans van der Wielen, Rick Helmus, John R Parsons, Eleni Gomes
The isolation of microorganisms from soil impacted by xenobiotic chemicals and exposing them in the laboratory to the contaminant can provide important information about their response to the contaminants. The purpose of this study was to isolate bacteria from soil with historical application of herbicides and to evaluate their potential to degrade diuron. The isolation media contained either glucose or diuron as carbon source. A total of 400 bacteria were isolated, with 68% being Gram-positive and 32% Gram-negative...
December 2017: Heliyon
https://www.readbyqxmd.com/read/29305508/comparative-transcriptome-analysis-reveals-the-mechanism-underlying-3-5-dibromo-4-hydroxybenzoate-catabolism-via-a-new-oxidative-decarboxylation-pathway
#9
Kai Chen, Yang Mu, Shanshan Jian, Xiaoxia Zang, Qing Chen, Weibin Jia, Zhuang Ke, Yanzheng Gao, Jiandong Jiang
The compound 3,5-dibromo-4-hydroxybenzoate (DBHB) is both anthropogenically released into and naturally produced in the environment, and its environmental fate is of great concern. Aerobic and anaerobic reductive dehalogenations are the only two reported pathways for DBHB catabolism. In this study, a new oxidative-decarboxylation pathway for DBHB catabolism was identified in a DBHB-utilizing strain of Pigmentiphaga sp. H8. The genetic determinants underlying this pathway were elucidated based on comparative transcriptome analysis and subsequent experimental validation...
January 5, 2018: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/29283566/interaction-mode-and-regioselectivity-in-vitamin-b12-dependent-dehalogenation-of-aryl-halides-by-dehalococcoides-mccartyi-strain-cbdb1
#10
Shangwei Zhang, Lorenz Adrian, Gerrit Schüürmann
The bacterium Dehalococcoides, strain CBDB1, transforms aromatic halides through reductive dehalogenation. So far, however, the structures of its vitamin B12-containing dehalogenases are unknown, hampering clarification of the catalytic mechanism and substrate specificity as basis for targeted remediation strategies. This study employs a quantum chemical donor-acceptor approach for the Co(I)-substrate electron transfer. Computational characterization of the substrate electron affinity at carbon-halogen bonds enables discriminating aromatic halides ready for dehalogenation by strain CBDB1 (active substrates) from non-dehalogenated (inactive) counterparts with 92% accuracy, covering 86 of 93 bromobenzenes, chlorobenzenes, chlorophenols, chloroanilines, polychlorinated biphenyls, and dibenzo-p-dioxins...
December 28, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/29282557/regioselective-alkali-metal-reduction-of-dibenzocyclooctadiene-lignan-derivatives-demethoxylation-followed-by-dehalogenation
#11
Qing-Yao Wang, Jia-Qi Fang, Lu-Lu Deng, Xiao-Jiang Hao, Shu-Zhen Mu
The regioselective demethoxylation and dehalogenation of dihalogenated dibenzocyclooctadiene lignans derivatives were realized in a one-step reaction with excellent yields in the sodium and t-butanol reaction system.
December 27, 2017: Chemistry Central Journal
https://www.readbyqxmd.com/read/29281267/capture-and-reductive-transformation-of-halogenated-pesticides-by-an-activated-carbon-based-electrolysis-system-for-treatment-of-runoff
#12
Yuanqing Li, William A Mitch
This study evaluates an electrochemical system to treat the halogenated pesticides, fipronil, permethrin and bifenthrin, in urban runoff. Compared to the poor sorption capacity of metal-based electrodes, granular activated carbon (GAC)-based electrodes could sorb halogenated pesticides, permitting electrochemical degradation to occur over longer timescales than reactor hydraulic residence times. In a dual-cell configuration, a cathode constructed of loose GAC containing sorbed pesticides was separated from the anode by an ion exchange membrane to prevent chloride transport and oxidation to chlorine at the anode...
December 27, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/29276812/highly-stereoselective-construction-of-halogenated-cyclic-quaternary-carbon-centers-via-br%C3%A3-nsted-base-catalyzed-4-2-cycloaddition-of-%C3%AE-haloaldehydes
#13
Qiang Li, Liang Zhou, Xu-Dong Shen, Kai-Chuan Yang, Xiang Zhang, Qing-Song Dai, Hai-Jun Leng, Qing-Zhu Li, Jun-Long Li
Asymmetric construction of halogenated quaternary carbon centers under mild conditions remains challenging. Here we report an unprecedented highly stereoselective, Brønsted base-catalyzed [4+2] cycloaddition between α-chloro- or α-bromoaldehydes and cyclic enones. The key intermediate, α-halogenated enolate, is susceptible to dehalogenation and can be stabilized and stereochemically controlled using bifunctional tertiary amines. This method provides facile access to a collection of optically pure bicyclic dihydropyrans with three contiguous stereocenters, including a halogen-bearing quaternary carbon center...
December 24, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/29273747/residues-his172-and-lys238-are-essential-for-the-catalytic-activity-of-the-maleylacetate-reductase-from-sphingobium-chlorophenolicum-strain-l-1
#14
Lifeng Chen, Ed S Krol, Meena K Sakharkar, Haseeb A Khan, Abdullah S Alhomida, Jian Yang
Maleylacetate reductase (PcpE), the last enzyme in the pentachlorophenol biodegradation pathway in Sphingobium chlorophenolicum L-1, catalyzes two consecutive reductive reactions, reductive dehalogenation of 2-chloromaleylacetate (2-CMA) to maleylacetate (MA) and subsequent reduction of MA to 3-oxoadipate (3-OXO). In each reaction, one molecule of NADH is consumed. To better understand its catalytic function, we undertook a structural model-based site-directed mutagenesis and steady-state kinetics study of PcpE...
December 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29259088/homoacetogenesis-in-deep-sea-chloroflexi-as-inferred-by-single-cell-genomics-provides-a-link-to-reductive-dehalogenation-in-terrestrial-dehalococcoidetes
#15
Holly L Sewell, Anne-Kristin Kaster, Alfred M Spormann
The deep marine subsurface is one of the largest unexplored biospheres on Earth and is widely inhabited by members of the phylum Chloroflexi In this report, we investigated genomes of single cells obtained from deep-sea sediments of the Peruvian Margin, which are enriched in such Chloroflexi 16S rRNA gene sequence analysis placed two of these single-cell-derived genomes (DscP3 and Dsc4) in a clade of subphylum I Chloroflexi which were previously recovered from deep-sea sediment in the Okinawa Trough and a third (DscP2-2) as a member of the previously reported DscP2 population from Peruvian Margin site 1230...
December 19, 2017: MBio
https://www.readbyqxmd.com/read/29243409/thermophilic-bacterial-communities-inhabiting-the-microbial-mats-of-indifferent-and-chalybeate-iron-rich-thermal-springs-diversity-and-biotechnological-analysis
#16
Ramganesh Selvarajan, Timothy Sibanda, Memory Tekere
Microbial mats are occasionally reported in thermal springs and information on such mats is very scarce. In this study, microbial mats were collected from two hot springs (Brandvlei (BV) and Calitzdorp (CA)), South Africa and subjected to scanning electron microscopy (SEM) and targeted 16S rRNA gene amplicon analysis using Next Generation Sequencing (NGS). Spring water temperature was 55°C for Brandvlei and 58°C for Calitzdorp while the pH of both springs was slightly acidic, with an almost identical pH range (6...
December 15, 2017: MicrobiologyOpen
https://www.readbyqxmd.com/read/29232478/customizing-photoredox-properties-of-pxx-based-dyes-through-energy-level-rigid-shifts-of-frontier-molecular-orbitals
#17
Andrea Sciutto, Andrea Fermi, Andrea Folli, Tommaso Battisti, Joseph Beames, Damien Murphy, Davide Bonifazi
Here we describe the synthesis of electron-rich PXX derivatives in which the energy levels of the excited states have been tailored through the insertion of imide groups. This has allowed the development of a new series of oxygen-doped photoredox-active chromophores with improved oxidizing and reducing properties. Capitalizing on the dehalogenation of organic halides as a model reaction, we could investigate the photooxidative and photoreductive potential of these molecules in model chemical transformations...
December 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29228161/reductive-tetrachloroethene-dehalogenation-in-the-presence-of-oxygen-by-sulfurospirillum-multivorans-physiological-studies-and-proteome-analysis
#18
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
#19
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
#20
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
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