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Penghui Du, He Zhao, Chenming Liu, Qingguo Huang, Hongbin Cao
The transformation of captopril (CAP), a widely-used thiol drug, was studied with the presence of dissolved model humic constituents (HCs) in a laccase-catalyzed system. Reaction products were analyzed by ultra-performance liquid chromatography coupled to time-of-flight mass spectrometry and condensed fukui function computation. CAP reacted with different model HCs in the enzymatic system for 1 h, ranging from 75% (syringic acid) to 96% (p-coumaric acid). In the absence of HCs, only 15% of CAP was removed through self-coupling...
October 14, 2016: Water Research
Marilia N Siebert, Jacó J Mattos, Clei E Piazza, Daína de Lima, Carlos Henrique A M Gomes, Cláudio M R de Melo, Afonso C D Bainy
Cytochrome P450 family 1 (CYP1) is involved in polycyclic aromatic hydrocarbons (PAHs) biotransformation. PAHs can induce CYP1 protein expression and enzyme activity, the latter being usually quantified as 7-ethoxyresorufin O-deethylase activity (EROD). The aim of this study was to characterize EROD activity in the bivalve mollusk Crassostrea brasiliana. EROD activity was evaluated in cytosolic and microsomal fractions of gills, digestive gland and mantle of C. brasiliana. No EROD activity was detected in mantle, but it was present in microsomal fraction of gills and digestive gland with NADPH as coenzyme...
October 18, 2016: Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology
Dennis Walczyk, Markus Gößringer, Walter Rossmanith, Timofei S Zatsepin, Tatiana S Oretskaya, Roland K Hartmann
Ribonuclease P (RNase P) is the enzyme that endonucleolytically removes 5'-precursor sequences from tRNA transcripts in all domains of life. RNase P activities are either ribonucleoprotein (RNP) or protein-only (PRORP) enzymes, raising the question about the mechanistic strategies utilized by these architecturally different enzyme classes to catalyze the same type of reaction. Here we analyzed the kinetics and cleavage-site selection by PRORP3 from Arabidopsis thaliana (AtPRORP3) using precursor tRNAs (pre-tRNAs) with individual modifications at the canonical cleavage site, either Rp- or Sp-phosphorothioate, or 2'-deoxy, 2'-fluoro, 2'-amino or 2'-O-methyl substitutions...
October 18, 2016: Journal of Molecular Biology
Elena Sugrue, Paul D Carr, Colin Scott, Colin J Jackson
The desolvation of ionizable residues in the active sites of enzymes and the subsequent effects on catalysis and thermostability have been studied in model systems, yet little is known regarding how enzymes can naturally evolve active sites with highly reactive and desolvated charges. Variants of triazine hydrolase (TrzN) with significant differences in their active sites have been isolated from different bacterial strains: TrzN from Nocardioides sp. strain MTD22 contains a catalytic glutamate residue (Glu241) that is surrounded by hydrophobic and aromatic second-shell residues (Pro214, Tyr215), whereas TrzN from Nocardioides sp...
October 21, 2016: Biochemistry
Ruhuai Mei, Cuiju Zhu, Lutz Ackermann
C-H arylations of weakly coordinating benzoic acids were achieved by versatile ruthenium(ii) catalysis with ample substrate scope. Thus, user-friendly ruthenium(ii) biscarboxylate complexes modified with tricyclohexylphosphine enabled C-H functionalizations with aryl electrophiles. The unique versatility of the ruthenium(ii) catalysis manifold was reflected by facilitating effective C-H activations with aryl, alkenyl and alkynyl halides.
October 21, 2016: Chemical Communications: Chem Comm
Deborah Brazzolotto, Marcello Gennari, Nicolas Queyriaux, Trevor R Simmons, Jacques Pécaut, Serhiy Demeshko, Franc Meyer, Maylis Orio, Vincent Artero, Carole Duboc
Hydrogen production through water splitting is one of the most promising solutions for the storage of renewable energy. [NiFe] hydrogenases are organometallic enzymes containing nickel and iron centres that catalyse hydrogen evolution with performances that rival those of platinum. These enzymes provide inspiration for the design of new molecular catalysts that do not require precious metals. However, all heterodinuclear NiFe models reported so far do not reproduce the Ni-centred reactivity found at the active site of [NiFe] hydrogenases...
November 2016: Nature Chemistry
Hong-Xin Liu, Ya-Qian Dang, Yun-Fei Yuan, Zhi-Fang Xu, Sheng-Xiang Qiu, Hai-Bo Tan
A general and excellent acylation reagent, diacyl disulfide, was uncovered for efficient ester formation enabled by DMAP (4-(N,N-dimethylamino)pyridine) catalysis. This protocol offered a promising synthetic platform on site-selective acylation of phenolic and primary aliphatic hydroxyl groups, which greatly expanded the realm of protecting group chemistry. The importance of the reagent was also reflected by its excellent moisture tolerance, high efficiency, and potential in synthetic chemistry and biologically meaningful natural product modification...
October 21, 2016: Organic Letters
Ettore J Rastelli, Ngoc T Truong, Don M Coltart
A new strategy for the rhodium-catalyzed enantioselective hydroacylation is described. This has been achieved through the merger of iminium ion catalysis and transition-metal catalysis such that asymmetric induction derives from a readily accessible, inexpensive chiral nonracemic secondary amine catalyst rather than a chiral nonracemic phosphine as is typical of conventional asymmetric hydroacylation methods.
October 21, 2016: Organic Letters
Xiaotong Cao, Jianquan Luo, John M Woodley, Yinhua Wan
Micro-pollutants present in water have many detrimental effects on the ecosystem. Membrane technology plays an important role in the removal of micro-pollutants but there remain significant challenges such as concentration polarization, membrane fouling and variable permeate quality. The work reported here uses a multifunctional membrane with rejection, adsorption and catalysis functions to solve these problems. Based on mussel-inspired chemistry and biological membrane properties, a multifunctional membrane was prepared by applying 'reverse filtration' of a laccase solution and subsequent 'dopamine coating' on a nanofiltration (NF) membrane support, which was tested on bisphenol A (BPA) removal...
October 21, 2016: ACS Applied Materials & Interfaces
M Ibrahim, M A S Garcia, L L R Vono, M Guerrero, P Lecante, L M Rossi, K Philippot
The solution synthesis of rhodium nanoparticles (Rh NPs) was achieved from the organometallic complex [Rh(η(3)-C3H5)3] under mild reaction conditions in the presence of a polymer (PVP), a monophosphine (PPh3) and a diphosphine (dppb) as a stabilizer, leading to very small Rh NPs of 2.2, 1.3 and 1.7 nm mean size, with PVP, PPh3 and dppb, respectively. The surface properties of these nanoparticles were compared using a model catalysis reaction namely, hydrogenation of cyclohexene, first under colloidal conditions and then under supported conditions after their immobilization onto an amino functionalized silica-coated magnetite support...
October 21, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Yongjin He, Jingbo Li, Sitharam Kodali, Bilian Chen, Zheng Guo
Dramatic decline in the quality and quantity of ω-3 PUFAs from marine resource demands new environmental-friendly technology to produce high quality ω-3 PUFAs concentrates in a better bioavailable form. Accordingly this work demonstrated an exceptionally highly efficient non-aqueous approach that non-regiospecific and non ω-3 PUFAs preferential Candida antarctica lipase A (CAL-A), functioning as a near-ideal biocatalyst, is capable to directly concentrate ω-3 PUFAs from 20% to 30% in oils to up to >90% in monoacylglycerols form through one step reaction...
March 15, 2017: Food Chemistry
Jean-Paul Lange
When investigating a new catalytic reaction, scientists may wonder if the crude reaction product can be easily separated and purified. We present here a new concept-distillation resistance-to assess the potential of distillation as a purification technique and to guide catalyst formulation or operation at the very early stage of the research. Distillation resistance, which has been developed from the analysis of 15 industrial distillation trains, can be quickly calculated with knowledge of only the product composition and atmospheric boiling points of the components...
October 20, 2016: ChemSusChem
Michael H Wang, Karl A Scheidt
N-Heterocyclic carbene (NHC) catalysis has emerged as a powerful stratagem in organic synthesis to construct complex molecules primarily by polarity reversal (umpolung) approaches. These unique Lewis bases have been used to generate acyl anions, enolates, and homoenolates in catalytic fashion. Recently, a new strategy has emerged that dramatically expands the synthetic utility of carbene catalysis by leveraging additional activation modes: cooperative catalysis. The careful selection and balance of cocatalysts have led to enhanced reactivity, increased yields, and improved stereoselectivity...
October 20, 2016: Angewandte Chemie
Parthasarathi Dastidar, Koushik Sarkar
A mixed ligand approach was exploited to synthesize a new series of MnII based coordination polymers (CPs), namely, CP1 {[Mn(-dpa)(-4,4-bp)]MeOH}α, CP2 {[Mn3(-dpa)3(2,2-bp)2]}α, CP3 {[Mn3(-dpa)3(1,10-phen)2]2H2O}α, CP4 {[Mn(-dpa)(-4,4-bpe)1.5]H2O}α, CP5 {[Mn2(-dpa)2(-4,4-bpe)2]½DEF}α and CP6 {[Mn(-dpa)(-4,4-bpe)1.5]½DMA}α, [dpa = 3,5-dicarboxy phenyl azide, 2,2-bp = 2,2-bipyridine, 1,10-phen = 1,10-phenanthroline, 4,4-bpe = 1,2-bis(4-pyridyl)ethylene, 4,4-bp = 4,4-bipyridine, DEF = N,N-diethylformamide, DMA = N,N-dimethylacetamide] to develop multifuntional CPs...
October 20, 2016: Chemistry: a European Journal
Yan Yan Li, Xin Yu Ming Dong, Xiaodan Sun, Ying Wang, Jian Hua Zhu
To fabricate new solid base with high efficiency in adsorption of CO2 at 473 K and catalytic activity in degradation of nitrosamines, magnesium oxalate and copper nitrate were mixed with assistance of microwave irradiation followed by calcination to immobilize CuO among MgO particles. The binary solid base CuO-MgO is thus moderately reduced to form the Cu inserted MgO composite with highly exposed strong basic sites, and it can capture 34.6 mg g(-1) of CO2 in the harsh instantaneous adsorption at 473 K and keep a high strong basicity to trap the CO2 mixed with SO2 and NO...
October 20, 2016: ACS Applied Materials & Interfaces
Ariel Lewis-Ballester, Farhad Forouhar, Sung-Mi Kim, Scott Lew, YongQiang Wang, Shay Karkashon, Jayaraman Seetharaman, Dipanwita Batabyal, Bing-Yu Chiang, Munif Hussain, Maria Almira Correia, Syun-Ru Yeh, Liang Tong
Tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) play a central role in tryptophan metabolism and are involved in many cellular and disease processes. Here we report the crystal structure of human TDO (hTDO) in a ternary complex with the substrates L-Trp and O2 and in a binary complex with the product N-formylkynurenine (NFK), defining for the first time the binding modes of both substrates and the product of this enzyme. The structure indicates that the dioxygenation reaction is initiated by a direct attack of O2 on the C2 atom of the L-Trp indole ring...
October 20, 2016: Scientific Reports
Jizhe Sun, Huimin Yu, Jie Chen, Hui Luo, Zhongyao Shen
Rhodococcus ruber TH was selected as a parent strain to engineer for biomanufacturing of ammonium acrylate; the characteristics of this strain included accelerated growth rate, high cell tolerance and natively overexpressed nitrile hydratase (NHase). Transcriptome analysis revealed that the transcription levels of the native NHase, amidase and nitrilase were extremely high, moderate and extremely low, respectively. Through NHase-amidase double-knockout and amidase single-knockout, the engineered strains R. ruber THdAdN and R...
October 19, 2016: Journal of Industrial Microbiology & Biotechnology
Somasundaram Ramasamy, Mohammad Mahfuzul Haque, Mahinda Gangoda, Dennis J Stuehr
The NO synthases (NOS) catalyze a two-step oxidation of L-Arginine (Arg) to generate NO. In the first step, O2 activation involves one electron being provided to the heme by an enzyme-bound 6R-tetrahydro-L-biopterin cofactor (H4 B), which then forms a H4 B radical that must be reduced back to H4 B in order for NOS to continue catalysis. Although an NADPH-derived electron is used to reduce the H4 B radical, how this occurs is unknown. We hypothesized that the NOS flavoprotein domain might reduce the H4 B radical by utilizing the NOS heme porphyrin as a conduit to deliver the electron...
October 19, 2016: FEBS Journal
Elisabetta Alberico, Alastair J J Lennox, Lydia K Vogt, Haijun Jiao, Wolfgang Baumann, Hans-Joachim Drexler, Martin Nielsen, Anke Spannenberg, Marek P Checinski, Henrik Junge, Matthias Beller
Ruthenium PNP complex 1a (RuH(CO)Cl(HN(C2H4Pi-Pr2)2)) represents a state-of-the-art catalyst for low-temperature (<100 °C) aqueous methanol dehydrogenation to H2 and CO2. Herein, we describe an investigation that combines experiment, spectroscopy and theory to provide a mechanistic rationale for this process. During catalysis, the presence of two anionic resting states was revealed, Ru-dihydride (3-) and Ru-monohydride (4-) that are deprotonated at nitrogen in the pincer ligand backbone. DFT calculations showed that O- and CH- coordination modes of methoxide to ruthenium compete, and form complexes 4- and 3-, respectively...
October 19, 2016: Journal of the American Chemical Society
Shogo Okumura, Shu-Wei Tang, Teruhiko Saito, Kazuhiko Semba, Shigeyoshi Sakaki, Yoshiaki Nakao
We report a method that ensures the selective alkylation of benzamides and aromatic ketones at the para-position via cooperative nickel/aluminum catalysis. Using a bulky catalyst/co-catalyst system allows reactions between benzamides with alkenes to afford the corresponding para-alkylated products. The origin of the high para-selectivity has also been investigated by density functional theory calculations.
October 19, 2016: Journal of the American Chemical Society
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