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https://www.readbyqxmd.com/read/27711866/the-role-of-ammonia-in-promoting-ammonia-borane-synthesis
#1
P Veeraraghavan Ramachandran, Ameya S Kulkarni
Ammonia promotes the synthesis of pure ammonia borane (AB) in excellent yields from sodium borohydride and ammonium sulfate in tetrahydrofuran under ambient conditions. An examination of the influence of added ammonia reveals that it is incorporated into the product AB, contrary to its perceived function as a catalyst or a co-solvent. Mechanistic studies point to a nucleophilic attack by ammonia on ammonium borohydride with concurrent dehydrogenation to yield AB.
October 18, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/27669648/anammox-biochemistry-a-tale-of-heme-c-proteins
#2
Boran Kartal, Jan T Keltjens
Anaerobic ammonium-oxidizing (anammox) bacteria are one of the latest scientific discoveries in the biogeochemical nitrogen cycle. These microorganisms are able to oxidize ammonium (NH4(+)) with nitrite (NO2(-)) as the oxidant instead of oxygen and form dinitrogen (N2) as the end product. Recent research has shed a light on the biochemistry underlying anammox metabolism with two key intermediates, nitric oxide (NO) and hydrazine (N2H4). Substrates and intermediates are converted exploiting the catalytic and electron-transfer potentials of c-type heme proteins known from numerous biochemical reactions and that have acquired new functionality in anammox biochemistry...
September 23, 2016: Trends in Biochemical Sciences
https://www.readbyqxmd.com/read/27529725/metal-free-alternating-copolymerization-of-co2-with-epoxides-fulfilling-green-synthesis-and-activity
#3
Dongyue Zhang, Senthil K Boopathi, Nikos Hadjichristidis, Yves Gnanou, Xiaoshuang Feng
Polycarbonates were successfully synthesized for the first time through the anionic copolymerization of epoxides with CO2, under metal-free conditions. Using an approach based on the activation of epoxides by Lewis acids and of CO2 by appropriate cations, well-defined alternating copolymers made of CO2 and propylene oxide (PO) or cyclohexene oxide (CHO) were indeed obtained. Triethyl borane was the Lewis acid chosen to activate the epoxides, and onium halides or onium alkoxides involving either ammonium, phosphonium, or phosphazenium cations were selected to initiate the copolymerization...
September 7, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27461995/membrane-bound-electron-transport-systems-of-an-anammox-bacterium-a-complexome-analysis
#4
Naomi M de Almeida, Hans J C T Wessels, Rob M de Graaf, Christina Ferousi, Mike S M Jetten, Jan T Keltjens, Boran Kartal
Electron transport, or oxidative phosphorylation, is one of the hallmarks of life. To this end, prokaryotes evolved a vast variety of protein complexes, only a small part of which have been discovered and studied. These protein complexes allow them to occupy virtually every ecological niche on Earth. Here, we applied the method of proteomics-based complexome profiling to get a better understanding of the electron transport systems of the anaerobic ammonium-oxidizing (anammox) bacteria, the N2-producing key players of the global nitrogen cycle...
October 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27317665/characterization-of-anammox-hydrazine-dehydrogenase-a-key-n2-producing-enzyme-in-the-global-nitrogen-cycle
#5
Wouter J Maalcke, Joachim Reimann, Simon de Vries, Julea N Butt, Andreas Dietl, Nardy Kip, Ulrike Mersdorf, Thomas R M Barends, Mike S M Jetten, Jan T Keltjens, Boran Kartal
Anaerobic ammonium-oxidizing (anammox) bacteria derive their energy for growth from the oxidation of ammonium with nitrite as the electron acceptor. N2, the end product of this metabolism, is produced from the oxidation of the intermediate, hydrazine (N2H4). Previously, we identified N2-producing hydrazine dehydrogenase (KsHDH) from the anammox organism Kuenenia stuttgartiensis as the gene product of kustc0694 and determined some of its catalytic properties. In the genome of K. stuttgartiensis, kustc0694 is one of 10 paralogs related to octaheme hydroxylamine (NH2OH) oxidoreductase (HAO)...
August 12, 2016: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/27017580/ammonium-aminodiboranate-a-long-sought-isomer-of-diammoniate-of-diborane-and-ammonia-borane-dimer
#6
Weidong Chen, Haibo Yu, Guotao Wu, Teng He, Zhao Li, Zaiping Guo, Huakun Liu, Zhenguo Huang, Ping Chen
Ammonium aminodiboranate ([NH4 ][BH3 NH2 BH3 ]) is a long-sought isomer of diammoniate of diborane ([NH3 BH2 NH3 ][BH4 ]) and ammonia borane (NH3 BH3 ) dimer. Our results show that [NH4 ][BH3 NH2 BH3 ] is stable in tetrahydrofuran at -18 °C and decomposes rapidly to NH3 BH2 NH2 BH3 and H2 at elevated temperatures. The decomposition pathway is dictated by the dihydrogen bonding between H(δ+) on NH4 (+) and H(δ-) on BH3 , as confirmed by theoretical calculations. This is in contrast to the interconversion between [NH3 BH2 NH3 ][BH4 ] and (NH3 BH3 )2 , although all three have dihydrogen bonds and the same stoichiometry...
June 1, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/26610025/complete-nitrification-by-a-single-microorganism
#7
Maartje A H J van Kessel, Daan R Speth, Mads Albertsen, Per H Nielsen, Huub J M Op den Camp, Boran Kartal, Mike S M Jetten, Sebastian Lücker
Nitrification is a two-step process where ammonia is first oxidized to nitrite by ammonia-oxidizing bacteria and/or archaea, and subsequently to nitrate by nitrite-oxidizing bacteria. Already described by Winogradsky in 1890, this division of labour between the two functional groups is a generally accepted characteristic of the biogeochemical nitrogen cycle. Complete oxidation of ammonia to nitrate in one organism (complete ammonia oxidation; comammox) is energetically feasible, and it was postulated that this process could occur under conditions selecting for species with lower growth rates but higher growth yields than canonical ammonia-oxidizing microorganisms...
December 24, 2015: Nature
https://www.readbyqxmd.com/read/26568531/metagenomic-analysis-of-anammox-communities-in-three-different-microbial-aggregates
#8
Jianhua Guo, Yongzhen Peng, Lu Fan, Liang Zhang, Bing-Jie Ni, Boran Kartal, Xin Feng, Mike S M Jetten, Zhiguo Yuan
There is great potential to understand the functional diversity of microorganisms that are involved in waste water treatment through metagenomic analyses. This study presents the first metagenomic comparison of taxonomic and functional profiles of the microbial communities occurring in different aggregates from anaerobic ammonium-oxidizing (anammox) bioreactors. The anammox bacterial communities in both biofilm and granule sludge samples showed relatively high abundance and diversity compared with floccular sludge...
September 2016: Environmental Microbiology
https://www.readbyqxmd.com/read/26493512/scope-and-mechanisms-of-frustrated-lewis-pair-catalyzed-hydrogenation-reactions-of-electron-deficient-c-c-double-bonds
#9
Varvara Morozova, Peter Mayer, Guillaume Berionni
Several phosphonium and ammonium triarylborohydrides, which are intermediates in hydrogenation reactions catalyzed by frustrated Lewis pairs, were synthesized in high yield under mild conditions from triaryl boranes, ammonium or phosphonium halides, and triethylsilane. The kinetics and mechanisms of the reactions of these hydridoborate salts with benzhydrylium ions, iminium ions, quinone methides, and Michael acceptors were investigated, and their nucleophilicity was determined and compared with that of other hydride donors...
November 23, 2015: Angewandte Chemie
https://www.readbyqxmd.com/read/26479033/the-inner-workings-of-the-hydrazine-synthase-multiprotein-complex
#10
Andreas Dietl, Christina Ferousi, Wouter J Maalcke, Andreas Menzel, Simon de Vries, Jan T Keltjens, Mike S M Jetten, Boran Kartal, Thomas R M Barends
Anaerobic ammonium oxidation (anammox) has a major role in the Earth's nitrogen cycle and is used in energy-efficient wastewater treatment. This bacterial process combines nitrite and ammonium to form dinitrogen (N2) gas, and has been estimated to synthesize up to 50% of the dinitrogen gas emitted into our atmosphere from the oceans. Strikingly, the anammox process relies on the highly unusual, extremely reactive intermediate hydrazine, a compound also used as a rocket fuel because of its high reducing power...
November 19, 2015: Nature
https://www.readbyqxmd.com/read/26096811/synthesis-of-periphery-decorated-and-core-initiated-borane-polyanionic-macromolecules
#11
Francesc Teixidor, Ariadna Pepiol, Clara Viñas
A new class of globular polybranched macromolecules that contain multiple anionic metallacarborane clusters at the o-carborane periphery is reported. The water soluble high boron rich containing molecules could be of interest for boron neutron capture therapy (BNCT) as well as for drug delivery. The reinforced electrostatic noncovalent interactions between anionic polyethylene glycol cobaltabisdicarbollide (PEG-COSAN) branches and the ammonium cation have been shown using ESI-MS.
July 20, 2015: Chemistry: a European Journal
https://www.readbyqxmd.com/read/26016548/reactivity-of-amine-e-c6f5-3-e-b-al-lewis-pairs-toward-linear-and-cyclic-acrylic-monomers-hydrogenation-vs-polymerization
#12
Jiawei Chen, Eugene X-Y Chen
This work reveals the contrasting reactivity of amine/E(C6F5)3 (E = B, Al) Lewis pairs toward linear and cyclic acrylic monomers, methyl methacrylate (MMA) and biorenewable γ-methyl-α-methylene-γ-butyrolactone (γMMBL). While mixing of 2,2,6,6-tetramethylpiperidine (TMP) and B(C6F5)3 leads to a frustrated Lewis pair (FLP), Et3N reacts with B(C6F5)3 to form disproportionation products, ammonium hydridoborate ionic pair and iminium zwitterion. On the other hand, the stoichiometric reaction of either TMP or Et3N with Al(C6F5)3 leads to clean formation of a classic Lewis adduct (CLA)...
2015: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/26010677/open-flask-synthesis-of-amine-boranes-via-tandem-amine-ammonium-salt-equilibration-metathesis
#13
P Veeraraghavan Ramachandran, Ameya S Kulkarni
An amine-ammonium salt equilibration-metathesis sequence provides high-purity amine-boranes in excellent yields from sodium borohydride in refluxing reagent-grade tetrahydrofuran in an open flask.
June 15, 2015: Inorganic Chemistry
https://www.readbyqxmd.com/read/25962914/immunogold-localization-of-key-metabolic-enzymes-in-the-anammoxosome-and-on-the-tubule-like-structures-of-kuenenia-stuttgartiensis
#14
Naomi M de Almeida, Sarah Neumann, Rob J Mesman, Christina Ferousi, Jan T Keltjens, Mike S M Jetten, Boran Kartal, Laura van Niftrik
UNLABELLED: Anaerobic ammonium-oxidizing (anammox) bacteria oxidize ammonium with nitrite as the terminal electron acceptor to form dinitrogen gas in the absence of oxygen. Anammox bacteria have a compartmentalized cell plan with a central membrane-bound "prokaryotic organelle" called the anammoxosome. The anammoxosome occupies most of the cell volume, has a curved membrane, and contains conspicuous tubule-like structures of unknown identity and function. It was suggested previously that the catalytic reactions of the anammox pathway occur in the anammoxosome, and that proton motive force was established across its membrane...
July 2015: Journal of Bacteriology
https://www.readbyqxmd.com/read/25962786/anammox-planctomycetes-have-a-peptidoglycan-cell-wall
#15
Muriel C F van Teeseling, Rob J Mesman, Erkin Kuru, Akbar Espaillat, Felipe Cava, Yves V Brun, Michael S VanNieuwenhze, Boran Kartal, Laura van Niftrik
Planctomycetes are intriguing microorganisms that apparently lack peptidoglycan, a structure that controls the shape and integrity of almost all bacterial cells. Therefore, the planctomycetal cell envelope is considered exceptional and their cell plan uniquely compartmentalized. Anaerobic ammonium-oxidizing (anammox) Planctomycetes play a key role in the global nitrogen cycle by releasing fixed nitrogen back to the atmosphere as N2. Here using a complementary array of state-of-the-art techniques including continuous culturing, cryo-transmission electron microscopy, peptidoglycan-specific probes and muropeptide analysis, we show that the anammox bacterium Kuenenia stuttgartiensis contains peptidoglycan...
2015: Nature Communications
https://www.readbyqxmd.com/read/25822613/delocalization-of-charge-and-electron-density-in-the-humulyl-cation%C3%A2-implications-for-terpene-biosynthesis
#16
Trevor A Hamlin, Christian S Hamann, Dean J Tantillo
The stabilizing features of a macrocyclic sesquiterpene-derived cation were explored using quantum mechanical calculations. The monocyclic humulyl cation, the product of 11,1-cyclization of farnesyl diphosphate, is the product of the first committed step in the enzymatic synthesis of a range of structurally diverse sesquiterpenes, including humulene (monocyclic); caryophyllene (bicyclic); and protoilludene, pentalenene, and isocomene (tricyclic). These natural products are formed via carbocation cascades that are directed in part by the conformation of the humulyl cation...
April 17, 2015: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/25287816/isolation-and-characterization-of-a-prokaryotic-cell-organelle-from-the-anammox-bacterium-kuenenia-stuttgartiensis
#17
Sarah Neumann, Hans J C T Wessels, W Irene C Rijpstra, Jaap S Sinninghe Damsté, Boran Kartal, Mike S M Jetten, Laura van Niftrik
Anaerobic ammonium oxidizing (anammox) bacteria oxidize ammonium with nitrite to nitrogen gas in the absence of oxygen. These microorganisms form a significant sink for fixed nitrogen in the oceans and the anammox process is applied as a cost-effective and environment-friendly nitrogen removal system from wastewater. Anammox bacteria have a compartmentalized cell plan that consists of three separate compartments. Here we report the fractionation of the anammox bacterium Kuenenia stuttgartiensis in order to isolate and analyze the innermost cell compartment called the anammoxosome...
November 2014: Molecular Microbiology
https://www.readbyqxmd.com/read/24750895/interactions-between-anaerobic-ammonium-and-sulfur-oxidizing-bacteria-in-a-laboratory-scale-model-system
#18
Lina Russ, Daan R Speth, Mike S M Jetten, Huub J M Op den Camp, Boran Kartal
Fixed nitrogen is released by anaerobic ammonium oxidation (anammox) and/or denitrification from (marine) ecosystems. Nitrite, the terminal electron acceptor of the anammox process, occurs in nature at very low concentrations and is produced via (micro)aerobic oxidation of ammonium or nitrate reduction. The coupling of sulfide-dependent denitrification to anammox is particularly interesting because besides hydrogen, sulfide is the most important reductant at the chemocline of anoxic marine basins and is abundant within sediments...
November 2014: Environmental Microbiology
https://www.readbyqxmd.com/read/24738410/interleaved-mesoporous-copper-for-the-anode-catalysis-in-direct-ammonium-borane-fuel-cells
#19
Francis M Auxilia, Toyokazu Tanabe, Shinsuke Ishihara, Govindachetty Saravanan, Gubbala V Ramesh, Futoshi Matsumoto, Xu Ya, Katsuhiko Ariga, Arivuoli Dakshanamoorthy, Hideki Abe
Mesoporous materials with tailored microstructures are of increasing importance in practical applications particularly for energy generation and/or storage. Here we report a mesoporous copper material (MS-Cu) can be prepared in a hierarchical microstructure and exhibit high catalytic performance for the half-cell reaction of direct ammonium borane (NH3BH3) fuel cells (DABFs). Hierarchical copper oxide (CuO) nanoplates (CuO Npls) were first synthesized in a hydrothermal condition. CuO Npls were then reduced at room temperature using water solution of sodium borohydride (NaBH4) to yield the desired mesoporous copper material, MS-Cu, consisting of interleaved nanoplates with a high density of mesopores...
June 2014: Journal of Nanoscience and Nanotechnology
https://www.readbyqxmd.com/read/24302732/structural-basis-of-biological-no-generation-by-octaheme-oxidoreductases
#20
Wouter J Maalcke, Andreas Dietl, Sophie J Marritt, Julea N Butt, Mike S M Jetten, Jan T Keltjens, Thomas R M Barends, Boran Kartal
Nitric oxide is an important molecule in all domains of life with significant biological functions in both pro- and eukaryotes. Anaerobic ammonium-oxidizing (anammox) bacteria that contribute substantially to the release of fixed nitrogen into the atmosphere use the oxidizing power of NO to activate inert ammonium into hydrazine (N2H4). Here, we describe an enzyme from the anammox bacterium Kuenenia stuttgartiensis that uses a novel pathway to make NO from hydroxylamine. This new enzyme is related to octaheme hydroxylamine oxidoreductase, a key protein in aerobic ammonium-oxidizing bacteria...
January 17, 2014: Journal of Biological Chemistry
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