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https://www.readbyqxmd.com/read/28346937/in-crystal-reaction-cycle-of-a-toluene-bound-diiron-hydroxylase
#1
Justin F Acheson, Lucas J Bailey, Thomas C Brunold, Brian G Fox
Electrophilic aromatic substitution is one of the most important and recognizable classes of organic chemical transformation. Enzymes create the strong electrophiles that are needed for these highly energetic reactions by using O2, electrons, and metals or other cofactors. Although the nature of the oxidants that carry out electrophilic aromatic substitution has been deduced from many approaches, it has been difficult to determine their structures. Here we show the structure of a diiron hydroxylase intermediate formed during a reaction with toluene...
March 27, 2017: Nature
https://www.readbyqxmd.com/read/28346909/bioaugmentaton-in-technosols-created-in-abandoned-pyritic-tailings-can-contribute-to-enhance-soil-c-sequestration-and-plant-colonization
#2
Raúl Zornoza, Melisa Gómez-Garrido, Silvia Martínez-Martínez, María Dolores Gómez-López, Ángel Faz
Creation of Technosols in combination with phytostabilization may be a sustainable strategy to minimize the environmental and human health hazards derived from mine tailings. Bioaugmentation can facilitate plant establishment and growth for efficient phytostabilization. In order to assess if bioaugmentation can increase soil quality and fertility, decrease metal(loid) mobility and accelerate plant colonization, a one-year field experiment was designed with creation of Technosols in two tailings ponds with different pH (acidic (AT) and neutral (NT)), with addition of marble waste (MaW) and two organic materials (pig manure (PM) and sewage sludge (SS), without or with inoculation of effective microorganisms (EM) at three rates...
March 24, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28346904/single-particle-mass-spectral-signatures-from-vehicle-exhaust-particles-and-the-source-apportionment-of-on-line-pm2-5-by-single-particle-aerosol-mass-spectrometry
#3
Jian Yang, Shexia Ma, Bo Gao, Xiaoying Li, Yanjun Zhang, Jing Cai, Mei Li, Ling'ai Yao, Bo Huang, Mei Zheng
In order to accurately apportion the many distinct types of individual particles observed, it is necessary to characterize fingerprints of individual particles emitted directly from known sources. In this study, single particle mass spectral signatures from vehicle exhaust particles in a tunnel were performed. These data were used to evaluate particle signatures in a real-world PM2.5 apportionment study. The dominant chemical type originating from average positive and negative mass spectra for vehicle exhaust particles are EC species...
March 24, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28346902/in-situ-synthesis-of-cobalt-ferrites-embedded-hollow-n-doped-carbon-as-an-outstanding-catalyst-for-elimination-of-organic-pollutants
#4
Tao Zeng, Mingdong Yu, Haiyan Zhang, Zhiqiao He, Xiaole Zhang, Jianmeng Chen, Shuang Song
Using polydopamine-metal ions complex as precursor, hollow mesoporous N-doped carbon microspheres encapsulating spinel ferrites nanocrystals (HM-NC/CoFe2O4) were facilely prepared with the aim of creating a novel heterogeneous catalyst for sulfate radical-based oxidation of organic contaminants. The surface morphology, structure and composition of HM-NC/CoFe2O4 catalyst were thoroughly investigated. The applicability of the catalyst was systematically assessed through numerous controlled trials, several operating parameters, as well as different model pollutants by means of peroxymonosulfate (PMS) activation...
March 24, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28346828/chemical-transformation-of-colloidal-nanostructures-with-morphological-preservation-by-surface-protection-with-capping-ligands
#5
Wenjing Xu, Mingsheng Wang, Zhiwei Li, Xiaojing Wang, Yongqiang Wang, Mingyang Xing, Yadong Yin
When nanocrystals are made to undergo chemical transformations, there are often accompanying large mechanical deformations and changes to overall particle morphology. These effects can constrain development of multi-step synthetic methods through loss of well-defined particle morphology and functionality. Here, we demonstrate a surface protection strategy for solution phase chemical conversion of colloidal nanostructures that allows for preservation of overall particle morphology despite large volume changes...
March 27, 2017: Nano Letters
https://www.readbyqxmd.com/read/28346827/effects-of-cerium-oxide-and-ferrocene-nanoparticles-addition-as-fuel-borne-catalysts-on-diesel-engine-particulate-emissions-environmental-and-health-implications
#6
Zhi-Hui Zhang, Rajasekhar Balasubramanian
This study systematically examined the potential impacts of doping CeO2 and Fe(C5H5)2 nanoparticles as fuel-borne catalysts (FBCs) to ultralow sulfur diesel (ULSD) fuel on the physical, chemical and toxicological characteristics of diesel particulate matter (DPM). The FBCs-doped fuels are effective in promoting soot oxidation and reducing the DPM mass emissions, but lead to a significant increase in the total particle counts due to the formation of self-nucleated metallic nanoparticles. Compared to undoped ULSD, the FBCs-doped fuels result in higher concentrations of particle-phase polycyclic aromatic hydrocarbons (PAHs) and n-alkanes, higher fractions of organic carbon (OC) and water-soluble organic carbon (WSOC) in particles, show slight alterations in soot nanostructure, reduce soot ignition temperature and activation energy...
March 27, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28346826/imaging-successive-intermediate-states-of-the-on-surface-ullmann-reaction-on-cu-111-role-of-the-metal-coordination
#7
Sören Zint, Daniel Ebeling, Tobias Schlöder, Sebastian Ahles, Doreen Mollenhauer, Hermann A Wegner, Andre Schirmeisen
The in-depth knowledge about on-surface reaction mechanisms is crucial for the tailor-made design of covalently bonded organic frameworks, for applications such as nanoelectronic or -optical devices. Latest developments in atomic force microscopy, which rely on functionalizing the tip with single CO molecules at low temperatures allow to image molecular systems with submolecular resolution. Here, we are using this technique to study the complete reaction pathway of the on-surface Ullmann-type coupling between bromotriphenylene molecules on a Cu(111) surface...
March 27, 2017: ACS Nano
https://www.readbyqxmd.com/read/28346744/radiopaque-uhmwpe-sublaminar-cables-for-spinal-deformity-correction-preclinical-mechanical-and-radiopacifier-leaching-assessment
#8
Alex K Roth, Karlien Boon-Ceelen, Harold Smelt, Bert van Rietbergen, Paul C Willems, Lodewijk W van Rhijn, Jacobus J Arts
Polymeric sublaminar cables have a number of advantages over metal cables in the field of spinal deformity surgery, with decreased risk of neurological injury and potential for higher correction forces as the two most predominant. However, currently available polymer cables are radiolucent, precluding postoperative radiological assessment of instrumentation stability and integrity. This study provides a preclinical assessment of a woven UHMWPE cable made with radiopaque UHMWPE fibers. Our primary goal was to determine if the addition of a radiopacifier negatively affects the mechanical properties of UHMWPE woven cables...
March 27, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
https://www.readbyqxmd.com/read/28346554/fundamental-insights-into-interfacial-catalysis
#9
EDITORIAL
Jinlong Gong, Xinhe Bao
Surface and interfacial catalysis plays a vital role in chemical industries, electrochemistry and photochemical reactions. The challenges of modern chemistry are to optimize the chemical reaction processes and understand the detailed mechanism of chemical reactions. Since the early 1960s, the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level, and thus brought a number of significant developments to fundamental and technological processes, such as catalysis, material science and biochemistry, just to name a few...
March 27, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28346432/nanoscale-capillary-freezing-of-ionic-liquids-confined-between-metallic-interfaces-and-the-role-of-electronic-screening
#10
Jean Comtet, Antoine Niguès, Vojtech Kaiser, Benoit Coasne, Lydéric Bocquet, Alessandro Siria
Room-temperature ionic liquids (RTILs) are new materials with fundamental importance for energy storage and active lubrication. They are unusual liquids, which challenge the classical frameworks of electrolytes, whose behaviour at electrified interfaces remains elusive, with exotic responses relevant to their electrochemical activity. Using tuning-fork-based atomic force microscope nanorheological measurements, we explore here the properties of confined RTILs, unveiling a dramatic change of the RTIL towards a solid-like phase below a threshold thickness, pointing to capillary freezing in confinement...
March 27, 2017: Nature Materials
https://www.readbyqxmd.com/read/28346388/thermal-condensation-of-glycine-and-alanine-on-metal-ferrite-surface-primitive-peptide-bond-formation-scenario
#11
Md Asif Iqubal, Rachana Sharma, Sohan Jheeta, Kamaluddin
The amino acid condensation reaction on a heterogeneous mineral surface has been regarded as one of the important pathways for peptide bond formation. Keeping this in view, we have studied the oligomerization of the simple amino acids, glycine and alanine, on nickel ferrite (NiFe₂O₄), cobalt ferrite (CoFe₂O₄), copper ferrite (CuFe₂O₄), zinc ferrite (ZnFe₂O₄), and manganese ferrite (MnFe₂O₄) nanoparticles surfaces, in the temperature range from 50-120 °C for 1-35 days, without applying any wetting/drying cycles...
March 27, 2017: Life
https://www.readbyqxmd.com/read/28346218/wafer-scale-production-of-highly-uniform-two-dimensional-mos2-by-metal-organic-chemical-vapor-deposition
#12
TaeWan Kim, Jihun Mun, Hyeji Park, DaeHwa Joung, Mangesh Diware, Won Chegal, Jonghoo Park, Soo-Hwan Jeong, Sang-Woo Kang
Semiconducting two-dimensional (2D) materials, particularly, extremely thin molybdenum disulfide (MoS2) films are attracting considerable attention from the academia and industry owing to their distinctive optical and electrical properties. Here, we present the direct growth of a MoS2 monolayer with unprecedented spatial and structural uniformity across an entire 8-inch SiO2/Si wafer. The influences of growth pressure, ambient gases (Ar, H2), and S/Mo molar flow ratio on the MoS2 layered growth were explored by considering the domain size, nucleation sites, morphology, and impurity incorporation...
March 27, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28346215/enhanced-optoelectronic-quality-of-perovskite-films-with-excess-ch3nh3i-for-high-efficient-solar-cells-in-ambient-air
#13
Yunhai Zhang, Huiru Lv, Can Cui, Lingbo Xu, Peng Wang, Hao Wang, Xuegong Yu, Jiangsheng Xie, Jiabin Huang, Zeguo Tang, Deren Yang
The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity...
March 27, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28345930/palladium-catalyzed-formal-5-2-annulation-between-ortho-alkenylanilides-and-allenes
#14
Borja Cendón, Noelia Casanova, Cezar Comanescu, Rebeca García-Fandiño, Andrés Seoane, Moisés Gulías, José L Mascareñas
2-Alkenyltriflylanilides react with allenes upon treatment with catalytic amounts of Pd(OAc)2 and Cu(II) to give highly valuable 2,3-dihydro-1H-benzo[b]azepines, in good yields, and with very high regio- and diastereoselectivities. Density functional theory (DFT) calculations suggest that the C-H activation of the alkenylanilide involves a classical concerted metalation-deprotonation (CMD) mechanism.
March 27, 2017: Organic Letters
https://www.readbyqxmd.com/read/28345925/metal-insertion-in-a-methylamine-functionalized-zirconium-metal-organic-framework-for-enhanced-carbon-dioxide-capture
#15
A Paulina Gómora-Figueroa, Jarad A Mason, Miguel I Gonzalez, Eric D Bloch, Katie R Meihaus
The reaction of ZrCl4 with 2',3',5',6'-tetramethylamino-p-terphenyl-4,4″-dicarboxylic acid (H2tpdc-4CH2NH2·3HCl) in the presence of NaF affords Zr6O4(OH)2.1F1.9(tpdc-4CH2NH2·3HCl)6 (1), which is a new member of the Zr6O4(OH)4(dicarboxylate linker)12 or UiO-68 family, and exhibits high porosity with BET and Langmuir surface areas of 1910 m(2)/g and 2220 m(2)/g, respectively. Remarkably, fluoride ion incorporation in the zirconium clusters results in increased thermal stability, marking the first example of enhancement in the stability of a UiO framework by this defect-restoration approach...
March 27, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28345914/photoreductive-elimination-of-chlorine-from-antimony-in-an-sbpd-vii-complex
#16
Sumit Sahu, Francois P Gabbaï
As part of our ongoing interest in main group species that support the photoreductive elimination of halogens, we have synthesized [Cl3SbVPdIICl2(o-dppp)2] (2, o-dppp = o-(Ph2P)C6H4), a palladium dichloride complex featuring a Lewis acidic trichlorostiborane moiety positioned within the ligand architecture. Upon UV irradiation, this complex undergoes a clean photoreductive chlorine elimination reaction which produces [Cl2SbIVPdICl(o-dppp)2] (1), a complex with a covalent Sb-Pd bond. This transformation illustrates the viability of antimony as an element from which a halogen can be photoeliminated; it also shows that a metal halide can be photolytically coupled with a main group halide to generate a metal-element bond...
March 27, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28345908/rapid-low-temperature-formation-of-imine-linked-cofs-catalyzed-by-metal-triflates
#17
Michio Matsumoto, Raghunath R Dasari, Woojung Ji, Cameron H Feriante, Timothy C Parker, Seth R Marder, William R Dichtel
Imine-linked two-dimensional covalent organic frameworks (2D COFs) are crystalline polymer networks with enhanced stability and broader monomer scope compared to boronate ester-linked systems. They are traditionally prepared by condensing polyfunctional aldehydes and amines at elevated temperature in a mixture of organic solvents and aqueous CH3CO2H, which catalyzes imine formation and exchange. Under these conditions, an amorphous imine-linked polymer network precipitates quickly and then crystallizes after extended reaction times (hours to days)...
March 27, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28345907/simulating-protein-mediated-hydrolysis-of-atp-and-other-nucleoside-triphosphates-by-combining-qm-mm-molecular-dynamics-with-advances-in-metadynamics
#18
Rui Sun, Olaseni Sode, James F Dama, Gregory A Voth
The protein mediated hydrolysis of nucleoside triphosphates such as ATP or GTP is one of the most important and challenging biochemical reactions in nature. The chemical environment (water structure, catalytic metal, and amino acid residues) adjacent to the hydrolysis site contains hundreds of atoms, usually greatly limiting the amount of the free energy sampling that one can achieve from computationally demanding electronic structure calculations such as QM/MM simulations. Therefore, the combination of QM/MM molecular dynamics with the recently developed Transition-tempered Metadynamics (TTMetaD), an enhanced sampling method that can provide a high-quality free energy estimate at an early stage in a simulation, is an ideal approach to address the biomolecular nucleoside triphosphate hydrolysis problem...
March 27, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28345901/recyclable-single-component-rare-earth-metal-catalysts-for-cycloaddition-of-co2-and-epoxides-at-atmospheric-pressure
#19
Zhiwen Zhao, Jie Qin, Chen Zhang, Yaorong Wang, Dan Yuan, Yingming Yao
Ionic rare-earth metal complexes 1-4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO2. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60-97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40-95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity...
March 27, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28345899/ammonia-borane-dehydrogenation-catalyzed-by-%C3%AE%C2%BA-4-ep3-co-h-ep3-e-ch2ch2pph2-3-e-n-p-and-h2-evolution-from-their-interaction-with-nh-acids
#20
Stefano Todisco, Lapo Luconi, Giuliano Giambastiani, Andrea Rossin, Maurizio Peruzzini, Igor E Golub, Oleg A Filippov, Natalia V Belkova, Elena S Shubina
Two Co(I) hydrides containing the tripodal polyphosphine ligand EP3, (κ(4)-EP3)Co(H) [E(CH2CH2PPh2)3; E = N (1), P (2)], have been exploited as ammonia borane (NH3BH3, AB) dehydrogenation catalysts in THF solution at T = 55 °C. The reaction has been analyzed experimentally through multinuclear ((11)B, (31)P{(1)H}, (1)H) NMR and IR spectroscopy, kinetic rate measurements, and kinetic isotope effect (KIE) determination with deuterated AB isotopologues. Both complexes are active in AB dehydrogenation, albeit with different rates and efficiency...
March 27, 2017: Inorganic Chemistry
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