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Somayesadat Badieyan, Qiuming Wang, Xingquan Zou, Yaoxin Li, Maggie Herron, Nicholas L Abbott, Zhan Chen, E Neil G Marsh
In the absence of aqueous buffer most enzymes retain little or no activity; however, "water-free" enzymes would have many diverse applications. Here we describe the chemically precise immobilization of an enzyme on an engineered surface designed to support catalytic activity in air at ambient humidity. Covalent immobilization of haloalkane dehalogenase on a surface support displaying poly-(sorbitol methacrylate) chains resulted in ~ 40-fold increase in activity over lyophilized enzyme powders for the gas-phase dehalogenation of 1-bromopropane...
February 13, 2017: Journal of the American Chemical Society
Linus O Johannissen, David Leys, Sam Hay
Distinct mechanisms have been proposed for the biological dehalogenation catalyzed by cobalamin-dependent enzymes, with two recent crystallographic studies suggesting different mechanisms based on the observed interaction between the organohalide substrate and cobalamin. In one case, involving an aromatic dibromide substrate in NpRdhA, a novel Co(II)-Br interaction was observed using EPR, suggesting a mechanism involving a [CoXR] adduct. However, in the case of trichloroethylene in PceA, a significantly longer Co-Cl distance was observed in X-ray crystal structures, suggesting a dissociative electron transfer mechanism...
February 13, 2017: Physical Chemistry Chemical Physics: PCCP
Huihui Kong, Sha Yang, Hongying Gao, Alexander Timmer, Jonathan P Hill, Oscar Díaz Arado, Harry Mönig, Xinyan Huang, Qin Tang, Qingmin Ji, Wei Liu, Harald Fuchs
Intermolecular C-C coupling after cleavage of C-X (mostly, X = Br or I) bonds has been extensively studied for facilitating the synthesis of polymeric nanostructures. However, the accidental appearance of C-H coupling at the terminal carbon atoms would limit the successive extension of covalent polymers. To our knowledge, the selective C-H coupling after dehalogenation has not so far been reported, which may illuminate another interesting field of chemical synthesis on surfaces besides in-situ fabrication of polymers, i...
February 10, 2017: Journal of the American Chemical Society
Jennifer Bridwell-Rabb, Catherine L Drennan
The ability of cobalamin to coordinate different upper axial ligands gives rise to a diversity of reactivity. Traditionally, adenosylcobalamin is associated with radical-based rearrangements, and methylcobalamin with methyl cation transfers. Recently, however, a new role for adenosylcobalamin has been discovered as a light sensor, and a methylcobalamin-dependent enzyme has been identified that is suggested to transfer a methyl anion. Additionally, recent studies have provided a wealth of new information about a third class of cobalamin-dependent enzymes that do not appear to use an upper ligand...
February 3, 2017: Current Opinion in Chemical Biology
Nattha Ingavat, Jennifer M Kavran, Zuodong Sun, Steven E Rokita
The minimal requirements for substrate recognition and turnover by iodotyrosine deiodinase were examined to learn the basis for its catalytic specificity. This enzyme is crucial for iodide homeostasis and the generation of thyroid hormone in chordates. 2-Iodophenol binds only very weakly to the human enzyme and is dehalogenated with a kcat/Km that is more than 4-orders of magnitude lower than that for iodotyrosine. This discrimination likely protects against a futile cycle of iodinating and deiodinating precursors of thyroid hormone biosynthesis...
February 3, 2017: Biochemistry
Christopher B Kelly, Niki R Patel, David N Primer, Matthieu Jouffroy, John C Tellis, Gary A Molander
Visible-light-activated photoredox catalysts provide synthetic chemists with the unprecedented capability to harness reactive radicals through discrete, single-electron transfer (SET) events. This protocol describes the synthesis of two transition metal complexes, [Ir{dF(CF3)2ppy}2(bpy)]PF6 (1a) and [Ru(bpy)3](PF6)2 (2a), that are activated by visible light. These photoredox catalysts are SET agents that can be used to facilitate transformations ranging from proton-coupled electron-transfer-mediated cyclizations to C-C bond constructions, dehalogenations, and H-atom abstractions...
March 2017: Nature Protocols
Anita Hoang, Kirill Popov, Peter Somfai
Perophoramidine and communesin F are structurally related indole alkaloids with an intriguing polycyclic core containing vicinal all-carbon quaternary stereocenters. Dehaloperophoramidine is a dehalogenated synthetic analogue of perophoramidine. Synthetic studies toward the total synthesis of dehaloperophoramidine have led to the discovery of two novel domino processes, the first encompassing four steps and resulting in the formation of an ortho-amide. A thorough study of the reactivity of the ortho-amide functionality revealed the second domino reaction and ultimately yielded the target molecule...
February 8, 2017: Journal of Organic Chemistry
Trent A Key, Kimberly S Bowman, Imchang Lee, Jongsik Chun, Milton da Costa, Luciana Albuquerque, Fred A Rainey, William M Moe
A strictly anaerobic, Gram-stain-negative, non-spore-forming bacterium designated NSZ-14T, isolated from contaminated groundwater in Louisiana (USA), was characterized using a polyphasic approach. Strain NSZ-14T reductively dehalogenated a variety of polychlorinated aliphatic alkanes, producing ethene from 1,2-dichloroethane, propene from 1,2-dichloropropane, a mixture of cis- and trans-1,2-dichloroethene from 1,1,2,2-tetrachloroethane, vinyl chloride from 1,1,2-trichloroethane, and allyl chloride (3-chloro-1-propene) from 1,2,3-trichloropropane...
January 23, 2017: International Journal of Systematic and Evolutionary Microbiology
Vinayak Agarwal, Zachary D Miles, Jaclyn M Winter, Alessandra S Eustáquio, Abrahim A El Gamal, Bradley S Moore
Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution...
January 20, 2017: Chemical Reviews
Valentine Grimaudo, Pavel Moreno-García, Andreas Riedo, Stefan Meyer, Marek Tulej, Maike B Neuland, Miklós Mohos, Christoph Gütz, Siegfried R Waldvogel, Peter Wurz, Peter Broekmann
Femtosecond laser ablation/ionization mass spectrometry (LIMS) has been applied to probe the spatial element composition of three ternary Cu-Sn-Pb model bronze alloys (lead bronzes: CuSn10Pb10, CuSn7Pb15, and CuSn5Pb20), which were recently identified as high-performance cathode materials in the context of electro-organic synthesis (dehalogenation, deoxygenation) of pharmaceutically relevant building blocks. The quantitative and spatially resolved element analysis of such cathode materials will help in understanding the observed profound differences in their electrochemical reactivity and stability...
February 7, 2017: Analytical Chemistry
Uwe Rosenthal, Martha Hoehne, Markus Joksch, Katharina Konieczny, Bernd Harald Mueller, Anke Spannenberg, Normen Peulecke
To date a plethora of λ3-P nitrogen containing-compounds is known. A large part of them is used as ligands in coordination chemistry and homogeneous catalysis. PN-containing compounds tend to build up cyclic moieties which have received less attention in regard to their application as ligands in transition metal chemistry. Hence different dehalogenation reactions of N,N-Bis{chloro(aryl)-phosphino}-amines have being developed to synthesize different P-N-P containing cyclic compounds. Their coordination behaviour to group (VI) transition metal carbonyls was explored...
January 20, 2017: Chemistry: a European Journal
Filiz Karakas, Ipek Imamoglu
This study aims to estimate anaerobic debromination rate constants (km) of PBDE pathways using previously reported laboratory soil data. km values of pathways are estimated by modifying a previously developed model as Anaerobic Dehalogenation Model. Debromination activities published in the literature in terms of bromine substitutions as well as specific microorganisms and their combinations are used for identification of pathways. The range of estimated km values is between 0.0003 and 0.0241 d(-1). The median and maximum of km values are found to be comparable to the few available biologically confirmed rate constants published in the literature...
January 19, 2017: Bulletin of Environmental Contamination and Toxicology
Hanna R Temme, Kipp Sande, Tao Yan, Paige J Novak
: Organohalide respiring bacteria can be difficult to enrich and isolate, which can limit research on these important organisms. The goal of this research was to develop a method to rapidly (minutes to days) enrich these organisms from a mixed community. The method presented is based on the hypothesis that organohalide respiring bacteria would be more hydrophobic than other bacteria as they dehalogenate hydrophobic compounds. The developed method tests this hypothesis by separating a portion of putative organohalide respiring bacteria, those phylogenetically related to Dehalococcoides mccartyi, at the interface between a hydrophobic organic solvent and aqueous media...
January 13, 2017: Applied and Environmental Microbiology
Ye Ji Kim, Sun Min Kim, Chunghyeon Yu, YoungMin Yoo, Eun Jin Cho, Jung Woon Yang, Sung Wng Kim
Halogenated organic compounds are important anthropogenic chemicals widely used in chemical industry, biology, and pharmacology; however, the persistence and inertness of organic halides cause human health problems and considerable environmental pollution. Thus, the elimination or replacement of halogen atoms with organic halides has been considered a central task in synthetic chemistry. In dehalogenation reactions, the consecutive single-electron transfer from reducing agents generates the radical and corresponding carbanion and thus removes the halogen atom as the leaving group...
January 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Anandarup Goswami, Anuj K Rathi, Claudia Aparicio, Ondrej Tomanec, Martin Petr, Radka Pocklanova, Manoj B Gawande, Rajender S Varma, Radek Zboril
Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions...
January 11, 2017: ACS Applied Materials & Interfaces
Rui Wang, Guining Lu, Haozhong Lin, Kaibo Huang, Ting Tang, Xiuling Xue, Xingjian Yang, Hua Yin, Zhi Dang
The relative significance of H-atom transfer versus electron transfer in the dehalogenation of halogenated organic compounds (HOCs) in bimetallic systems has long been debated. In this study, we have investigated this question through the case study of the debromination of 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47). The debromination rates of isomer products of BDE-47 by palladized nano zero-valent iron (n-ZVI/Pd) in the same reactor were compared. The results confirmed a shift in the debromination pathway of BDE-47 when treated with unpalladized nano zero-valent iron (n-ZVI) vs...
March 2017: Environmental Pollution
Ying Pan, Juan Chen, Haichao Zhou, Shazia Farzana, Nora F Y Tam
The removal and degradation of polybrominated diphenyl ethers (PBDEs) in sediments are not clear. The vertical distribution of total and dehalogenating bacteria in sediment cores collected from a typical mangrove swamp in South China and their intrinsic degradation potential were investigated. These bacterial groups had the highest abundances in surface sediments (0-5cm). A 5-months microcosm experiment also showed that surface sediments had the highest rate to remove BDE-47 than deeper sediments (5-30cm) under anaerobic condition...
December 26, 2016: Marine Pollution Bulletin
Chu-Wen Yang, Ching-Chang Lee, His Ku, Bea-Ven Chang
This study evaluated decabromodiphenyl ether (BDE-209) anaerobic debromination and bacterial community changes in mangrove sediment. BDE-209 debromination rates were enhanced with zerovalent iron compared to without zerovalent iron in the sediment. BDE-209 debromination rates in microcosms constructed with sediments collected in autumn were higher than in microcosms constructed with sediments collected in spring and were higher at the Bali sampling site than the Guandu sampling site. The intermediate products resulting from the reductive debromination of BDE-209 in sediment were nona-BDE (BDE-206, BDE-207), octa-BDEs (BDE-196, BDE-197), hepta-BDEs (BDE-183, BDE-184, BDE-191), hexa-BDEs (BDE-137, BDE-138, BDE-154, BDE-157), penta-BDEs (BDE-85, BDE-99, BDE-100, BDE-126), tetra-BDEs (BDE-47, BDE-49, BDE-66, BDE-77), tri-BDEs (BDE-17, BDE-28), and di-BDEs (BDE-15)...
December 24, 2016: Environmental Science and Pollution Research International
Lukáš Jedinák, Renáta Zátopková, Hana Zemánková, Alena Šustková, Petr Cankař
The efficient Suzuki-Miyaura cross-coupling reaction of halogenated aminopyrazoles and their amides or ureas with a range of aryl, heteroaryl, and styryl boronic acids or esters has been developed. The method allowed incorporation of problematic substrates: aminopyrazoles bearing protected or unprotected pyrazole NH, as well as the free amino or N-amide group. Direct comparison of the chloro, bromo, and iodopyrazoles in the Suzuki-Miyaura reaction revealed that Br and Cl derivatives were superior to iodopyrazoles, as a result of reduced propensity to dehalogenation...
December 20, 2016: Journal of Organic Chemistry
Jiehong Guo, Zhuona Li, Prabha Ranasinghe, Solidea Bonina, Soheil Hosseini, Margaret B Corcoran, Colin Smalley, Karl J Rockne, Neil C Sturchio, John P Giesy, An Li
Polyhalogenated carbazoles (PHCZs) have been increasingly detected in the environment. Their similarities in chemical structure with legacy pollutants and their potential toxicity have caused increasing concern. In this work, 112 Ponar grab and 28 core sediment samples were collected from Lakes Michigan, Superior, and Huron, and a total of 26 PHCZs were analyzed along with unsubstituted carbazole using gas chromatography coupled with single- or triple-quadrupole mass spectrometry. Our results show that the total accumulation of PHCZs in the sediments of the upper Great Lakes is >3000 tonnes, orders of magnitude greater than those of polychlorinated biphenyls (PCBs) and decabromodiphenyl ether (BDE209)...
January 3, 2017: Environmental Science & Technology
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