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Qiaochong He, Chuanping Feng, Nan Chen, Dongqing Zhang, Tingting Hou, Jingwen Dai, Chunbo Hao, Bingchun Mao
In this study, characteristics of dissolved organic matter (DOM) and bacterial community structure in rice washing drainage (RWD)-based groundwater denitrification systems inoculated with and without seeding sludge were investigated. Complete nitrate removal was achieved with a maximum denitrification rate of 64.1 mg NO3 - -N·(gVSS·h)-1 . Analysis of three-dimension fluorescence excitation-emission matrix (FEEM) identified three main compositions of DOM associated with tryptophan protein-like, aromatic protein-like, and polycarboxylate humic acid-like substances in the inoculated system, while one composition associated with tryptophan protein-like substance in the un-inoculated system...
October 6, 2018: Chemosphere
Ling Mo, Jing Zheng, Ting Wang, Yun-Gang Shi, Biao-Juan Chen, Bin Liu, Yan-Hua Ma, Min Li, Li Zhuo, She-Jun Chen
Emerging and legacy hydrophobic pollutants, including halogenated flame retardants (HFRs), organophosphorus FRs (OPFRs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs), as well as polycyclic aromatic hydrocarbons (PAHs) were determined in coastal sediments of Hainan Island, southern China, where little information is known about their contamination. The HFRs were dominated by decabrominated diphenyl ethers (median = 1.32 ng/g) and novel decabromodiphenyl ethane (1.87 ng/g). HFR and PAH concentrations had similar spatial distributions, with higher levels in the river and near the estuary...
October 5, 2018: Chemosphere
Chelsea A O'Driscoll, Leah A Owens, Erica J Hoffmann, Madeline E Gallo, Amin Afrazi, Mei Han, John H Fechner, James J Schauer, Christopher A Bradfield, Joshua D Mezrich
BACKGROUND: Autoimmune diseases have increased in incidence and prevalence worldwide. While genetic predispositions play a role, environmental factors are a major contributor. Atmospheric particulate matter (PM) is a complex mixture composed of metals, nitrates, sulfates and diverse adsorbed organic compounds like polycyclic aromatic hydrocarbons (PAHs) and dioxins. Exposure to atmospheric PM aggravates autoimmune diseases such as type 1 diabetes, rheumatoid arthritis, multiple sclerosis, and systemic lupus erythematosus, among others...
October 1, 2018: Environmental Research
Shaoyang Hu, Tingting Gong, Qiming Xian, Junjie Wang, Jian Ma, Zhigang Li, Jinbao Yin, Beibei Zhang, Bin Xu
Iodinated disinfection byproducts (DBPs) are widely present in disinfected drinking waters and wastewater effluents, and they have drawn increasing concern owing to their high toxicity. To date, the reported iodinated DBPs mainly include aliphatic and aromatic ones, and iodinated trihalomethanes (THMs) and haloacetic acids (HAAs) are the most commonly detected aliphatic iodinated DBPs in disinfected waters. In this study, the formation of iodinated THMs and HAAs from aromatic iodinated DBPs during chloramination was investigated...
October 2, 2018: Water Research
Victorien Delannée, Sophie Langouët, Anne Siegel, Nathalie Théret
Heterocyclic aromatic amines (HAAs) are environmental and food contaminants that are classified as probable or possible carcinogens by the International Agency for Research on Cancer. Thirty different HAAs have been identified. However the metabolism of only three of them have been fully characterized in human hepatocytes: AαC (2-amino-9H-pyrido[2,3-b]indole), MeIQx (2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline) and PhIP (2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine). In this study, we use an integrative approach to accurately predict the biotransformation of 30 HAAs into DNA reactive and non DNA reactive compounds...
October 10, 2018: Toxicology Letters
Casper Wilkens, Manish K Tiwari, Helen Webb, Murielle Jam, Mirjam Czjzek, Birte Svensson
In the marine environment agar degradation is assured by bacteria that contain large agarolytic systems with enzymes acting in various endo- and exo-modes. Agarase A (AgaA) is an endo-glycoside hydrolase of family 16 considered to initiate degradation of agarose. Agaro-oligosaccharide binding at a unique surface binding site (SBS) in AgaA from Zobellia galactanivorans was investigated by computational methods in conjunction with a structure/sequence guided approach of site-directed mutagenesis probed by surface plasmon resonance binding analysis of agaro-oligosaccharides of DP 4-10...
October 13, 2018: Proteins
Min Zhou, Tao Zhu, Xiaohua Fei
The performance of oxytetracycline adsorption by untreated reed roots, stems and leaves, as well as the desugared reed roots, stems and leaves, was investigated with scanning electron microscopy, Fourier-transform infrared spectroscopy, elemental analysis and surface area analysis to understand the adsorption mechanism. The results showed that the adsorption capacities of untreated reed were 416.35 mg/kg for roots, 341.92 mg/kg for stems and 280.21 mg/kg for leaves, and can be increased significantly by a factor of 8⁻12 after desugarization...
October 11, 2018: International Journal of Environmental Research and Public Health
Michiya Fujiki, Julian R Koe, Takashi Mori, Yoshihiro Kimura
We report experimental tests of whether non-rigid, π -conjugated luminophores in the photoexcited ( S ₁) and ground ( S ₀) states dissolved in achiral liquids are mirror symmetrical by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopy. Herein, we chose ten oligofluorenes, eleven linear/cyclic oligo- p -arylenes, three binaphthyls and five fused aromatics, substituted with alkyl, alkoxy, phenyl and phenylethynyl groups and also with no substituents. Without exception, all these non-rigid luminophores showed negative-sign CPL signals in the UV-visible region, suggesting temporal generation of energetically non-equivalent non-mirror image structures as far-from equilibrium open-flow systems at the S₁ state...
October 11, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Meriem Debbabi, Vijaykumar D Nimbarte, Samia Chekir, Sarra Chortani, Anis Romdhane, Hichem Ben Jannet
Pyrimidine-fused compounds are of great interest for the discovery of potent bioactive agents. This study describes the synthesis of novel pyranopyrimidines 3a-f and pyranotriazolopyrimidines 4a-d derivatives via the cyclocondensation reaction of α-functionalized iminoether 2, which was obtained from 2-amino-3-cyanopyrane 1, with a series of primary aromatic amines and hydrazides, respectively. Structures of all synthesized compounds were established on the basis of spectroscopic methods including 1 H NMR, 13 C NMR and ES-HRMS...
October 5, 2018: Bioorganic Chemistry
Jama Ariai, Giacomo Saielli
We have investigated, using two-component relativistic density functional theory (DFT) at ZORA-SO-BP86 and ZORA-SO-PBE0 level, the occurrence of relativistic effects on the 1H, 13C, and 15N NMR chemical shifts of 1-methylpyridinium halides [MP][X] and 1-butyl-3-methylpyridinium trihalides [BMP][X3] ionic liquids (ILs) (X = Cl, Br, I) as a result of a non-covalent interaction with the heavy anions. Our results indicate a sizeable deshielding effect in ion pairs when the anion is I- and I3-. A smaller, though nonzero, effect is observed also with bromine while chlorine based anions do not produce an appreciable relativistic shift...
October 12, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Qing Jiang, Tao Tao, Hoa Phan, Yi Han, Tullimilli Y Gopalakrishna, Tun Seng Herng, Guangwu Li, Liu Yuan, Jun Ding, Chunyan Chi
Non-alternant, non-benzenoid π-conjugated polycyclic hydrocarbons (PHs) are expected to exhibit very different electronic properties from all-benzenoid PHs. Herein, we report the synthesis and physical properties of four derivatives (1a-b, 2a-b) of two azulene-fused s-indacene isomers, the diazuleno[2,1-a:2',1'-g]-s-indacene (DAI-1) and diazuleno[2,1-a:1',2'-h]-s-indacene (DAI-2). The backbone of both isomers contains 28 πe and is a 7-5-5-6-5-5-7 fused ring system. X-ray crystallographic analysis, NMR spectra, and theoretical calculations (ACID, NICS) reveal a structure with two aromatic azulene units fused with a central anti-aromatic s-indacene moiety...
October 12, 2018: Angewandte Chemie
Pirom Chenprakhon, Thanyaporn Wongnate, Pimchai Chaiyen
Many flavoenzymes catalyze hydroxylation of aromatic compounds especially phenolic compounds have been isolated and characterized. These enzymes can be classified as either single-component or two-component flavin dependent hydroxylases (monooxygenases). The hydroxylation reactions catalyzed by the enzymes in this group are useful for modifying the biological properties of phenolic compounds. This review aims to provide an in-depth discussion of the current mechanistic understanding of representative flavin-dependent monooxygenases including 3-hydroxy-benzoate 4-hydroxylase (PHBH, a single-component hydroxylase), 3-hydroxyphenylacetate 4-hydroxylase (HPAH, a two-component hydroxylase) and other monooxygenases which catalyze reactions in addition to hydroxylation, including 2-methyl-3-hydroxypyridine-5-carboxylate oxygenase (MHPCO, a single-component enzyme that catalyzes aromatic-ring cleavage), and HadA monooxygenase (a two-component enzyme that catalyzes additional group elimination reaction)...
October 12, 2018: Protein Science: a Publication of the Protein Society
Polytimi S Dimitriou, Alexander I Denesyuk, Toru Nakayama, Mark S Johnson, Konstantin Denessiouk
The alpha/beta-hydrolases (ABH) are among the largest structural families of proteins that are found in nature. Although they vary in their sequence and function, the ABH enzymes use a similar acid-base-nucleophile catalytic mechanism to catalyze reactions on different substrates. Because ABH enzymes are biocatalysts with a wide range of potential applications, protein engineering has taken advantage of their catalytic versatility to develop enzymes with industrial applications. This study is a comprehensive analysis of 40 ABH enzyme families focusing on two identified substructures: the nucleophile zone and the oxyanion zone, which coordinate the catalytic nucleophile and the residues of the oxyanion hole, and independently reported as critical for the enzymatic activity...
October 12, 2018: Protein Science: a Publication of the Protein Society
Weiwei Zi, Hong-Fa Wang, Shi-Yue Wang, Tian-Zhu Qin
We herein report a dual gold-catalyzed tetradehydro-Diels-Alder reactions for the synthesis of nitrogen-containing aromatic heterocycles. Under the catalysts system (IPrAuNTf2/DIPEA), indolines and carbazoles as well as other N-containing aromatic heterocycles were prepared in high yields with good functional group tolerance. Unlike the traditional thermal tetradehydro-Diels-Alder reactions, diluted reaction concentration and radical prohibitors are not required for this protocol. Experimental data support a mechanism involving gold vinylidene species, which undergoes a 6π electrocyclization, followed with 1,2-hydrogen shift...
October 12, 2018: Chemistry: a European Journal
Eric C Wu, Qinghui Ge, Eric A Arsenault, Nicholas H C Lewis, Natalie L Gruenke, Martin J Head-Gordon, Graham R Fleming
The relaxation from the lowest singlet excited state of the triphenylmethane dyes, crystal violet and malachite green, is studied via two-dimensional electronic-vibrational (2DEV) spectroscopy. After excitation of the dyes at their respective absorption maxima, the ensuing excited state dynamics are tracked by monitoring the C[double bond, length as m-dash]C aromatic stretch. With the aid of electronic structure calculations, the observed transitions in the 2DEV spectra are assigned to specific geometries and a detailed story of the evolution of the nuclear wavepacket as it diffuses on the excited state potential energy surface (PES) and ultimately passes through the conical intersection is developed...
October 12, 2018: Physical Chemistry Chemical Physics: PCCP
Agnieszka Koszucka, Adriana Nowak
Heterocyclic aromatic amines, acrylamide, 5-hydroxymethylfurfural, furan, polycyclic aromatic hydrocarbons, nitrosamines, acrolein, chloropropanols and chloroesters are generated toxicants formed in some foodstuffs, mainly starchy and protein-rich food during thermal treatment such as frying, roasting and baking. The formation of these chemical compounds is associated with development of aromas, colors and flavors. One of the challenges facing the food industry today is to minimize these toxicants without adversely affecting the positive attributes of thermal processing...
October 12, 2018: Critical Reviews in Food Science and Nutrition
Peter B Karadakov, David L Cooper
It is shown, on the example of the monocyclic cyclononatetraenyl cation, C₉H₉+, that the fully-variational optimization of modern ab initio wavefunctions based on spin-coupled generalized valence bond (SCGVB) theory vindicates, in a surprising level of detail, essential features of Heilbronner's ideas for the electronic structure of Möbius annulenes such as the arrangement of overlapping carbon 2p atomic orbitals along a Möbius strip, leading to a phase inversion between the first and last orbitals. In the SCGVB description, the aromaticity of this Möbius system with eight π electrons follows from the extensive resonance between VB structures...
October 12, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Jiacheng Lan, Yuchuan Sun, Daoxian Yuan
The concentration and fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated in a karst underground river system in southwest China. Groundwater, particles, and sediments from underground river, topsoil, and surface water were monitored, allowing establishment of a conceptual model of PAH transport at the watershed scale. The results showed that PAHs could be transported from the surface to the subsurface through two migration pathways, which were slow-flowing water in the karst fissure and fast-flowing water in conduits...
October 11, 2018: Environmental Science and Pollution Research International
Qin Yang, Tianyi Luo, Jianghong Yang, Huaguo Chen
The purpose of this study was to investigate polycyclic aromatic hydrocarbons (PAHs) accumulation in leaves of different plant species growing in the neighborhood of coal-fired power plant (CPP) and to identify potential bioindicators for PAHs pollution monitoring. The study was performed in 8 sites in the surrounding areas of CPP. PAHs concentrations in leaves of 21 plant species growing within 1 km of CPP ranged from 0.043 to 4.52 µg g-1 . A higher mean concentration of PAHs was found in leaves of perennial herbs and shrubs compared with annual herbs and trees...
October 11, 2018: Archives of Environmental Contamination and Toxicology
L M Vieira, J Rizzi, E V do Couto, D C Souza, P A L Ferreira, R Figueira, S Froehner
In the present study, the environmental changes over the past 100 years in the Cambé River watershed in Southern Brazil were investigated. For this, a sediment core was collected to examine the distribution of metals, polycyclic aromatic hydrocarbons (PAHs), and ecotoxicological markers. The core corresponds from 1914 to 2012, which was obtained by the decay of 210 Pb. Changes in the study area also were examined by: Geoaccumulation index (Igeo) and enrichment factor (EF), sediment quality guidelines (SGQs), and ethoxyresorufin-O-deethylase (EROD) activity in Poeciliopsis lucida hepatocellular carcinoma (PLHC-1) cells line...
October 11, 2018: Archives of Environmental Contamination and Toxicology
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