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https://www.readbyqxmd.com/read/28655113/application-of-enhanced-gas-chromatography-triple-quadrupole-mass-spectrometry-for-monitoring-petroleum-weathering-and-forensic-source-fingerprinting-in-samples-impacted-by-the-deepwater-horizon-oil-spill
#1
Puspa L Adhikari, Roberto L Wong, Edward B Overton
Accurate characterization of petroleum hydrocarbons in complex and weathered oil residues is analytically challenging. This is primarily due to chemical compositional complexity of both the oil residues and environmental matrices, and the lack of instrumental selectivity due to co-elution of interferences with the target analytes. To overcome these analytical selectivity issues, we used an enhanced resolution gas chromatography coupled with triple quadrupole mass spectrometry in Multiple Reaction Monitoring (MRM) mode (GC/MS/MS-MRM) to eliminate interferences within the ion chromatograms of target analytes found in environmental samples...
June 19, 2017: Chemosphere
https://www.readbyqxmd.com/read/28655112/real-time-monitoring-of-the-degradation-of-cu-ii-edta-in-h2o2-uv-using-illumination-assisted-droplet-spray-ionization-mass-spectrometry
#2
Hong Zhang, Na Li, Yingying Wang, Dandan Zhao, Jing He, Hong You, Jie Jiang
Illumination-assisted droplet spray ionization (IA-DSI) mass spectrometry was developed for in situ analysis and real-time monitoring of photolysis reactions. In IA-DSI, a photolysis reaction occurs on a corner of a cover slip positioned in front of a mass spectrometer, and the generated reaction intermediates are ionized via the corner and are directed to the inlet and analyzed by a mass spectrometer. IA-DSI is contaminant-free, low-cost and simple, and was demonstrated for in situ analysis and real-time monitoring of the degradation of Cu(II)-EDTA in H2O2/UV...
June 19, 2017: Chemosphere
https://www.readbyqxmd.com/read/28654324/conceptual-and-experimental-tools-to-understand-spatial-effects-and-transport-phenomena-in-nonlinear-biochemical-networks-illustrated-with-patchy-switching
#3
Rebecca R Pompano, Andrew H Chiang, Christian J Kastrup, Rustem F Ismagilov
Many biochemical systems are spatially heterogeneous and exhibit nonlinear behaviors, such as state switching in response to small changes in the local concentration of diffusible molecules. Systems as varied as blood clotting, intracellular calcium signaling, and tissue inflammation are all heavily influenced by the balance of rates of reaction and mass transport phenomena including flow and diffusion. Transport of signaling molecules is also affected by geometry and chemoselective confinement via matrix binding...
June 20, 2017: Annual Review of Biochemistry
https://www.readbyqxmd.com/read/28654295/liposomes-in-polymersomes-lips-multi-compartment-system-with-temperature-triggered-release
#4
Ariane Peyret, Emmanuel Ibarboure, Natassa Pippa, Sebastien Lecommandoux
Multi-compartmentalization is a key feature of eukaryotic cells, allowing separation and protection of species within the membrane walls. During the last years, several methods have been reported to afford synthetic multi-compartment lipidic or polymeric vesicles that mimic biological cells and that allow cascade chemical or enzymatic reactions within their lumen. We hereby report on the preparation and study of liposomes in polymersomes (LiPs) systems. We discuss on the loading and co-loading of lipidic nano-vesicles made of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dipentadecanoyl-sn-glycero-3-phosphocholine (diC15-PC), or 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) inside the lumen of giant poly(butadiene)-b-poly(ethylene oxide) (PBut-b-PEO) polymersomes...
June 27, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28654289/oxidation-of-natural-bioactive-flavonolignan-2-3-dehydrosilybin-an-electrochemical-and-spectral-study
#5
Romana Sokolova, Jana Kocabova, Petr Marhol, Jan Fiedler, David Biedermann, Jan Vacek, Vladimir Kren
The electrochemical oxidation of the natural antioxidant 2,3-dehydrosilybin (DHS) was investigated in acetonitrile. The spectral changes during two electron and two proton oxidation registered by in situ IR spectroelectrochemistry show that the electron transfer is followed by a subsequent chemical reaction with traces of water. A benzofuranone derivative (BF) is formed by ECEC (electron transfer - chemical reaction - electron transfer - chemical reaction) process at the potential of the first oxidation wave...
June 27, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28654267/ternary-silver-halide-nanocrystals
#6
Sasitha C Abeyweera, Kowsalya D Rasamani, Yugang Sun
Nanocrystalline silver halides (AgX) such as AgCl, AgBr, and AgI, a class of semiconductor materials with characteristics of both direct and indirect band gaps, represent the most crucial components in traditional photographic processing. The nanocrystal surfaces provide sensitivity specks that can turn into metallic silver, forming an invisible latent image, upon exposure to light. The photographic processing implies that the AgX nanoparticles possess unique properties. First, pristine AgX nanoparticles absorb light only at low efficiency to convert surface AgX into tiny clusters of silver atoms...
June 27, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28654237/light-induced-proton-pumping-with-a-semiconductor-vision-for-photoproton-lateral-separation-and-robust-manipulation
#7
Hanna M Maltanava, Sergey K Poznyak, Daria V Andreeva, Marcela C Quevedo, Alexandre C Bastos, João Tedim, Mario G S Ferreira, Ekaterina V Skorb
Energy transfer reactions are the key for living open systems, biological chemical networking and development of life inspired nanoscale machineries. It is a challenge to find simple reliable synthetic chemical networks providing a localization of the time dependent flux of matter. In this paper we look to photocatalytic reaction on TiO2 from different angle focusing on proton generation and introduce a reliable, minimal reagent consuming, stable inorganic light promoted proton pump. Localized illumination was applied to a TiO2 surface in solution for reversible spatially controlled "inorganic photoproton" isometric cycling, the lateral separation of water splitting reactions...
June 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28654236/closed-bipolar-electrodes-for-spatial-separation-of-h2-and-o2-evolution-during-water-electrolysis-and-the-development-of-high-voltage-fuel-cells
#8
Sean E Goodwin, Darren Anthony Walsh
Electrolytic water splitting could potentially provide clean hydrogen for a future 'Hydrogen Economy.' However, as hydrogen and oxygen are produced in close proximity to each other in water electrolysers, significant mixing of the gases can occur during electrolysis, with potentially dangerous consequences. Herein, we describe an electrochemical water-splitting cell, in which mixing of the electrogenerated gases is impossible. In our cell, separate hydrogen- and oxygen-evolving cells are connected electrically by a bipolar electrode in contact with an inexpensive dissolved redox couple (potassium ferricyanide/potassium ferricyanide)...
June 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28654230/synthesis-of-multifunctional-electrically-tunable-fluorine-doped-reduced-graphene-oxide-at-low-temperatures
#9
Faisal Shahzad, Shabi Abbas Zaidi, Chong Min Koo
Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m-1 than that of undoped rGO with an electrical conductivity of 195 S m-1. To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker...
June 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28654117/synthesis-and-biological-evaluation-of-novel-acyclic-and-cyclic-glyoxamide-based-derivatives-as-bacterial-quorum-sensing-and-biofilm-inhibitors
#10
Shashidhar Nizalapur, Onder Kimyon, Eugene Yee, Mohan M Bhadbhade, Mike Manefield, Mark Willcox, David StC Black, Naresh Kumar
Bacteria regulate the expression of various virulence factors and processes such as biofilm formation through a chemically-mediated communication mechanism called quorum sensing. Bacterial biofilms contribute to antimicrobial resistance as they can protect bacteria embedded in their matrix from the effects of antibiotics. Thus, developing novel quorum sensing inhibitors, which can inhibit biofilm formation, is a viable strategy to combat antimicrobial resistance. We report herein the synthesis of novel acyclic and cyclic glyoxamide derivatives via ring-opening reactions of N-acylisatins...
June 27, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28653962/a-proposed-simulation-method-for-directed-self-assembly-of-nanographene
#11
James Geraets, Jack Baldwin, Reidun Twarock, Yvette Hancock
A methodology for predictive kinetic self-assembly modeling of bottom-up chemical synthesis of nanographene is proposed. The method maintains physical transparency in using a novel array format to efficiently store molecule information and by using array operations to determine reaction possibilities. Within a minimal model approach, the parameter space for the bond activation energies (i.e., molecule functionalization) at fixed reaction temperature and initial molecule concentrations is explored. Directed self-assembly of nanographene from functionalized tetrabenzanthracene and benzene is studied with regions in the activation energy phase-space showing length-to-width ratio tunability...
June 27, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28652917/photocrosslinkable-biodegradable-hydrogels-with-controlled-cell-adhesivity-for-prolonged-sirna-delivery-to-hmscs-to-enhance-their-osteogenic-differentiation
#12
Minh Khanh Nguyen, Alexandra McMillan, Cong Truc Huynh, Daniel S Schapira, Eben Alsberg
Photocrosslinked, biodegradable hydrogels have been extensively investigated for biomedical applications, including drug delivery and tissue engineering. Here, dextran (DEX) was chemically modified with mono(2-acryloyloxyethyl) succinate (MAES) via an esterification reaction, resulting in macromers that could be photocrosslinked to form hydrolytically degradable hydrogels. Hydrogel swelling ratio and degradation rate were controlled by varying the degree of MAES modification. Thiolated cell adhesion peptides (GRGDSPC) were conjugated to acrylated dextran via thiol-acrylate reaction to regulate the interactions of human mesenchymal stem cells (hMSCs) with the photocrosslinkable hydrogels...
January 21, 2017: Journal of Materials Chemistry. B, Materials for Biology and Medicine
https://www.readbyqxmd.com/read/28652025/multiple-functionalities-of-reduced-flavin-in-the-non-redox-reaction-catalyzed-by-udp-galactopyranose-mutase
#13
REVIEW
Pablo Sobrado, John J Tanner
Flavin cofactors are widely used by enzymes to catalyze a broad range of chemical reactions. Traditionally, flavins in enzymes are regarded as redox centers, which enable enzymes to catalyze the oxidation or reduction of substrates. However, a new class of flavoenzyme has emerged over the past quarter century in which the flavin functions as a catalytic center in a non-redox reaction. Here we introduce the unifying concept of flavin hot spots to understand and categorize the mechanisms and reactivities of both traditional and noncanonical flavoenzymes...
June 23, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28651142/fast-pyrolysis-of-durian-durio-zibethinus-l-shell-in-a-drop-type-fixed-bed-reactor-pyrolysis-behavior-and-product-analyses
#14
Y L Tan, A Z Abdullah, B H Hameed
Durian shell (DS) was pyrolyzed in a drop-type fixed-bed reactor to study the physicochemical properties of the products. The experiment was carried out with different particle sizes (up to 5mm) and reaction temperatures (250-650°C). The highest bio-oil yield was obtained at 650°C (57.45wt%) with DS size of 1-2mm. The elemental composition and higher heating value of the feedstock, bio-oil (650°C), and bio-char (650°C) were determined and compared. The compositions of product gases were determined via gas chromatography with thermal conductivity detector...
June 23, 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28651108/synchronous-characterization-of-carbohydrates-and-ginsenosides-yields-deeper-insights-into-the-processing-chemistry-of-ginseng
#15
Shan-Shan Zhou, Jun Xu, Ming Kong, Ka-Man Yip, Jin-Di Xu, Hong Shen, Zhong-Zhen Zhao, Song-Lin Li, Hu-Biao Chen
Carbohydrates and ginsenosides in ginseng are biologically interrelated. Their synchronous analysis is therefore essential in chemical research on ginseng to characterize its "holistic" quality. Here we investigated the processing chemistry of red ginseng (RG), a ginseng product processed by water-steaming, for which both carbohydrates and ginsenosides were qualitatively and quantitatively determined through multiple analytical techniques. Results revealed that the steam-processing not only qualitatively and quantitatively altered the ginsenosides but also affected the polymeric carbohydrates via changing their physiochemical parameters, i...
June 19, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28650651/tuning-selectivity-of-co2-hydrogenation-reactions-at-the-metal-oxide-interface
#16
Shyam Kattel, Ping Liu, Jingguang G Chen
The chemical transformation of CO2 not only mitigates the anthropogenic CO2 emission into the earth's atmosphere but also produces carbon compounds that can be used as precursors for the production of chemicals and fuels. The activation and conversion of CO2 can be achieved on multifunctional catalytic sites available at the metal/oxide interface by taking advantage of the synergy between the metal nanoparticles and oxide support. Herein, we reviewed the recent progress in mechanistic studies of CO2 hydrogenation to C1 (CO, CH3OH and CH4) compounds on metal/oxide catalysts...
June 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28650616/cucurbit-6-uril-promoted-click-chemistry-for-protein-modification
#17
Joel A Finbloom, Kenneth Han, Clancy C Slack, Ariel L Furst, Matthew B Francis
Azide-alkyne cycloaddition is a powerful reaction for the formation of bioconjugates. When catalyzed by Cu(I) or strain promotion, this cycloaddition is considered to be a "click" reaction with many applications in chemical biology and materials science. We report a new type of azide-alkyne click chemistry for the synthesis of protein conjugates using cucurbit[6]uril (CB6) supramolecular chemistry. CB6-promoted azide-alkyne cycloaddition has been previously used for the synthesis of rotaxanes, but has not been applied to the development of complex bioconjugates...
June 26, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28650613/glucose-oxidase-polymer-nanogels-for-synergistic-cancer-starving-and-oxidation-therapy
#18
Wenguo Zhao, Jin Hu, Weiping Gao
Glucose oxidase (GOX) can convert glucose into gluconic acid and hydrogen peroxide (H2O2), which is potentially useful for synergistic cancer starving and oxidation therapy. Herein we demonstrate a glucose-responsive nanomedicine of GOX-polymer nanogels to regulate H2O2 production for synergistic melanoma starving and oxidation therapy. GOX-polymer nanogels showed glucose-responsive H2O2-generating activity in vitro, improved stability, and considerably enhanced tumor retention as compared to native GOX. More importantly, they exhibited high anti-melanoma efficacy and no obvious systemic toxicity, whereas native GOX was ineffective and systemically toxic at the same dose...
June 26, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28650525/thermal-synthesis-of-perchlorinated-oligosilanes-a-fresh-look-at-an-old-reaction
#19
Max C Holthausen, Felix Neumeyer, Julia I Schweizer, Lioba Meyer, Alexander G Sturm, Andor Nadj, Norbert Auner
A combined experimental and theoretical study of the high-temperature reaction of SiCl4 and elemental silicon is presented. The nature and reactivity of the product formed upon rapid cooling of the gaseous reaction mixture is investigated by comparison with defined model compounds, i.e. cyclo-Si5Cl10, n-Si5Cl12 and n-Si4Cl10. A DFT assessment provides mechanistic insight into the oligosilane formation. Experimental 29Si NMR investigations, supported by quantum-chemical 29Si NMR calculations, consistently show that the reaction product is composed of discrete molecular perchlorinated oligosilanes...
June 26, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28650499/silver-catalyzed-3-2-domino-reaction-an-efficient-strategy-to-synthesize-imidazole-5-carbaldehydes
#20
Changcheng Wang, Hangqi Jiang, Weifeng Chen, Jun Dong, Zhengwang Chen, Hua Cao
An unprecedented regioselective silver-catalyzed [3 + 2] domino reaction of amidines and ynals for the formation of C-N bonds has been developed. The reaction provided a new route to prepare imidazole-5-carbaldehydes which are important intermediates for the construction of fine chemicals. The reaction proceeds smoothly with a broad range of substrates to give imidazoles in good yields.
June 26, 2017: Organic & Biomolecular Chemistry
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