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Sunday A Adebusoye
Cupriavidus sp. strain SK-3, previously isolated on polychlorinated biphenyl mixtures, was found to aerobically utilize a wide spectrum of substituted aromatic compounds including 4-fluoro-, 4-chloro- and 4-bromobenzoic acids as a sole carbon and energy source. Other chlorobenzoic acid (CBA) congeners such as 2-, 3-, 2,3-, 2,5-, 3,4- and 3,5-CBA were all rapidly transformed to respective chlorocatechols (CCs). Under aerobic conditions, strain SK-3 grew readily on 4-CBA to a maximum concentration of 5 mM above which growth became impaired and yielded no biomass...
October 20, 2016: Biodegradation
Shanquan Wang, Siyuan Chen, Yu Wang, Adrian Low, Qihong Lu, Rongliang Qiu
Due to massive production and improper handling, organohalide compounds are widely distributed in subsurface environments, primarily in anoxic groundwater, soil and sediment. Compared to traditional pump-and-treat or dredging-and-disposal treatments, in situ remediation employing abiotic or biotic reductive dehalogenation represents a sustainable and economic solution for the removal of organohalide pollutants. Both nanoscale zero-valent iron (nZVI) and organohalide-respiring bacteria remove halogens through reductive dehalogenation and have been extensively studied and successfully applied for the in situ remediation of chloroethenes and other organohalide pollutants...
October 17, 2016: Biotechnology Advances
Valeria Ochoa-Herrera, Jim A Field, Antonia Luna-Velasco, Reyes Sierra-Alvarez
Perfluorooctane sulfonate (PFOS) and related perfluoroalkyl and polyfluoroalkyl substances (PFASs) are emerging contaminants that have been widely applied in consumer and industrial applications for decades. However, PFOS has raised public concern due to its high bioaccumulative character, environmental persistence, and toxicity. Shorter PFASs such as perfluorobutane sulfonate (PFBS) and polyfluoroalkyl compounds have been proposed as alternatives to PFOS but it is unclear whether these fluorinated substances pose a risk for public health and the environment...
September 14, 2016: Environmental Science. Processes & Impacts
L Szatkowski, M B Hall
The nickel(i) octaethylisobacteriochlorin anion ([OEiBCh-Ni((I))](-)) is commonly used as a synthetic model of cofactor F430 from Methyl-Coenzyme M Reductase. In this regard, experimental studies show that [OEiBCh-Ni((I))](-) can catalyze dehalogenation of aliphatic halides in DMF solution by a highly efficient SN2 reaction. To better understand this process, we constructed theoretical models of the dehalogenation of chloromethane by a simple nickel(i) isobacteriochlorin anion and compared its reactivity with that of similar Ni((I)) complexes with other porphyrin-derived ligands: porphyrin, chlorin, bactreriochlorin, hexahydroporphyrin and octahydroporphyrin...
September 28, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Xinlin Li, Shiling Zhao, Wei Zhang, Yansheng Liu, Rong Li
Ruthenium (Ru) nanoparticles (NPs) are supported on nitrogen-doped porous carbon (NPC) derived from metal-organic-framework (MOF) ZIF-8 for the first time. NPC is prepared by the direct carbonization of ZIF-8 crystals, which not only retains the original morphology of ZIF-8 but also provides a high surface area and stable chemical-physical properties. Ru NPs were supported by different methods. Four types of Ru-based catalysts are tested in the selective hydrogenation of p-chloronitrobenzene (p-CNB) and p-bromonitrobenzene (p-BNB) to haloanilines...
October 4, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Feng-Cheng Jia, Cheng Xu, Zhi-Wen Zhou, Qun Cai, Yan-Dong Wu, An-Xin Wu
An unusual benzannulation reaction has been realized by integrating intermolecular adol condensation with subsequent intramolercular base-promoted homolytic aromatic substitution. This novel cascade reaction provides a straightforward approach toward various naphtho-fused oxindoles from 2-halobenzaldehydes and indolin-2-ones in the presence of Cs2CO3 in DMSO. The enolates of indolin-2-ones as new and internal electron donors have been demonstrated to initiate intramolecular radical dehalogenative coupling.
October 4, 2016: Organic Letters
Abrahim El Gamal, Vinayak Agarwal, Imran Rahman, Bradley S Moore
Enzymes capable of performing dehalogenating reactions have attracted tremendous contemporary attention due to their potential application in the bioremediation of anthropogenic polyhalogenated persistent organic pollutants. Nature, in particular the marine environment, is also a prolific source of polyhalogenated organic natural products. The study of the biosynthesis of these natural products has furnished a diverse array of halogenation biocatalysts, but thus far no examples of dehalogenating enzymes have been reported from a secondary metabolic pathway...
October 12, 2016: Journal of the American Chemical Society
Yu Zhang, Jeffrey L Petersen, Carsten Milsmann
Titanium and zirconium complexes carrying two 2,6-bis(pyrrolyl)pyridine ligands have been synthesized and characterized. The neutral complexes Ti((Me)PDP)2 and Zr((Me)PDP)2 ((Me)PDP = 2,6-bis(5-methyl-3-phenyl-1H-pyrrol-2-yl)pyridine) show intense ligand-to-metal charge-transfer bands in the visible region and undergo multiple reversible redox events under highly reducing conditions. Zr((Me)PDP)2 exhibits photoluminescent behavior and its excited state can be quenched by mild reductants to generate a powerful electron transfer reagent with a ground state potential of -2...
October 12, 2016: Journal of the American Chemical Society
Abhishek Phatarphekar, Steven E Rokita
The flavoprotein iodotyrosine deiodinase (IYD) was first discovered in mammals through its ability to salvage iodide from mono- and diiodotyrosine, the by-products of thyroid hormone synthesis. Genomic information indicates that invertebrates contain homologous enzymes although their iodide requirements are unknown. The catalytic domain of IYD from Drosophila melanogaster has now been cloned, expressed and characterized to determine the scope of its potential catalytic function as a model for organisms that are not associated with thyroid hormone production...
September 19, 2016: Protein Science: a Publication of the Protein Society
Peter H Jacobse, Adri van den Hoogenband, Marc-Etienne Moret, Robertus J M Klein Gebbink, Ingmar Swart
The Ullmann coupling has been used extensively as a synthetic tool for the formation of C-C bonds on surfaces. Thus far, most syntheses made use of aryl bromides or aryl iodides. We investigated the applicability of an aryl chloride in the bottom-up assembly of graphene nanoribbons. Specifically, the reactions of 10,10'-dichloro-9,9'-bianthryl (DCBA) on Au(111) were studied. Using atomic resolution non-contact AFM, the structure of various coupling products and intermediates were resolved, allowing us to reveal the important role of the geometry of the intermediate aryl radicals in the formation mechanism...
October 10, 2016: Angewandte Chemie
Haiming Zhang, Lifeng Chi
Gold-organic hybrids can be prepared on gold substrates by on-surface dehalogenation of molecular precursors with multiple halogen substituents. Various contact geometries of covalent arylAu bonds are achieved by changing the halogen substituents in the bay or peri regions. Scanning tunneling microscopy/spectroscopy (STM/STS) investigations allow a better understanding of the structure/property relationships in various gold-aryl contacts. Recent progress on the synthesis, large-scale alignment, and STS measurement of gold-organic hybrids is described, ending with an emphasis on potential future applications, e...
September 15, 2016: Advanced Materials
Ian D Wilson, Jeremy K Nicholson
The gut microbiota has both direct and indirect effects on drug and xenobiotic metabolisms, and this can have consequences for both efficacy and toxicity. Indeed, microbiome-driven drug metabolism is essential for the activation of certain prodrugs, for example, azo drugs such as prontosil and neoprontosil resulting in the release of sulfanilamide. In addition to providing a major source of reductive metabolizing capability, the gut microbiota provides a suite of additional reactions including acetylation/deacylation, decarboxylation, dehydroxylation, demethylation, dehalogenation, and importantly, in the context of certain types of drug-related toxicity, conjugates hydrolysis reactions...
August 13, 2016: Translational Research: the Journal of Laboratory and Clinical Medicine
Xianbin Su, Ruihong Li, Jimmy S H Tsang
Biodegradation is an effective way to remove environmental pollutants haloacids, and haloacids uptake is an important step besides cytoplasmic dehalogenation. Previous study has identified a robust haloacids transport system in Burkholderia caribensis MBA4 with two homologous genes deh4p and dehp2 as major players. Both genes are inducible by monochloroacetate (MCA), and dehp2 is conserved among the Burkholderia genus with a two component system upstream. Here we show that dehp2 is not in the same operon with the upstream two component system, and fusion with lacZ confirmed the presence of MCA-inducible promoter activity in the 228bp upstream non-coding region of dehp2...
November 30, 2016: Gene
Daryl Staveness, Irene Bosque, Corey R J Stephenson
Harnessing visible light as the driving force for chemical transformations generally offers a more environmentally friendly alternative compared with classical synthetic methodology. The transition metal-based photocatalysts commonly employed in photoredox catalysis absorb efficiently in the visible spectrum, unlike most organic substrates, allowing for orthogonal excitation. The subsequent excited states are both more reducing and more oxidizing than the ground state catalyst and are competitive with some of the more powerful single-electron oxidants or reductants available to organic chemists yet are simply accessed via irradiation...
October 18, 2016: Accounts of Chemical Research
Megan B McConville, Terrance D Hubert, Christina K Remucal
The lampricides 3-trifluoromethyl-4-nitrophenol (TFM) and 2',5-dichloro-4'-nitrosalicylanilide (niclosamide) are directly added to many tributaries of the Great Lakes that harbor the invasive parasitic sea lamprey. Despite their long history of use, the fate of lampricides is not well understood. This study evaluates the rate and pathway of direct photodegradation of both lampricides under simulated sunlight. The estimated half-lives of TFM range from 16.6 ± 0.2 h (pH 9) to 32.9 ± 1.0 h (pH 6), while the half-lives of niclosamide range from 8...
September 20, 2016: Environmental Science & Technology
Siva Prasad Das, Rakesh Ganguly, Yongxin Li, Han Sen Soo
A growing number of halogenated organic compounds have been identified as hazardous pollutants. Although numerous advanced oxidative processes have been developed to degrade organohalide compounds, reductive and nucleophilic molecular approaches to dehalogenate organic compounds have rarely been reported. In this manuscript, we employ nickel(ii)-ate complexes bearing the o-phenylenebis(N-methyloxamide) (Me2opba) tetraanionic ligand as nucleophilic reagents that can react with alkyl halides (methyl up to the bulky isobutyl) by O-alkylation to give their respective imidate products...
September 14, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Anett Schallmey, Marcus Schallmey
Halohydrin dehalogenases are industrially relevant enzymes that catalyze the reversible dehalogenation of vicinal haloalcohols with formation of the corresponding epoxides. In the reverse reaction, also other negatively charged nucleophiles such as azide, cyanide, or nitrite are accepted besides halides to open the epoxide ring. Thus, novel C-N, C-C, or C-O bonds can be formed by halohydrin dehalogenases, which makes them attractive biocatalysts for the production of various β-substituted alcohols. Despite the fact that only five individual halohydrin dehalogenase enzyme sequences have been known until recently enabling their heterologous production, a large number of different biocatalytic applications have been reported using these enzymes...
September 2016: Applied Microbiology and Biotechnology
C U Moreno-Medina, Hector M Poggi-Varaldo, L Breton-Deval, N Rinderknecht-Seijas
The present work evaluated the effects of (i) feeding a water contaminated with 80 mg/L PCE to bioreactors seeded with inoculum not acclimated to PCE, (ii) coupling ZVI side filters to bioreactors, and (iii) working in different biological regimes, i.e., simultaneous methanogenic aeration and simultaneous methanogenic-denitrifying regimes, on fluidized bed bioreactor performance. Simultaneous electron acceptors refer to the simultaneous presence of two compounds operating as final electron acceptors in the biological respiratory chain (e...
August 8, 2016: Environmental Science and Pollution Research International
Hong Zhong, Caiping Liu, Hanghui Zhou, Yangxin Wang, Ruihu Wang
Three porous organic polymers (POPs) containing H, COOMe, and COO(-) groups at 2,6-bis(1,2,3-triazol-4-yl)pyridyl (BTP) units (i.e., POP-1, POP-2, and POP-3, respectively) were prepared for the immobilization of metal nanoparticles (NPs). The ultrafine palladium NPs are uniformly encapsulated in the interior pores of POP-1, whereas uniform- and dual-distributed palladium NPs are located on the external surface of POP-2 and POP-3, respectively. The presence of carboxylate groups not only endows POP-3 an outstanding dispersibility in H2 O/EtOH, but also enables the palladium NPs at the surface to show the highest catalytic activity, stability, and recyclability in dehalogenation reactions of chlorobenzene at 25 °C...
August 22, 2016: Chemistry: a European Journal
Emilie Lefevre, Ellen Cooper, Heather M Stapleton, Claudia K Gunsch
The increasing occurrence of tetrabromobisphenol A (TBBPA) in the environment is raising questions about its potential ecological and human health impacts. TBBPA is microbially transformed under anaerobic conditions to bisphenol A (BPA). However, little is known about which taxa degrade TBBPA and the adaptation of microbial communities exposed to TBBPA. The objectives of this study were to characterize the effect of TBBPA on microbial community structure during the start-up phase of a bench-scale anaerobic sludge reactor, and identify taxa that may be associated with TBBPA degradation...
2016: PloS One
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