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https://www.readbyqxmd.com/read/29786930/an-unexpected-%C3%AE-oxidation-of-cyclic-ketones-with-1-4-benzoquinone-via-enol-catalysis
#1
Benjamin List, Grigory A Shevchenko, Barry Oppelaar
The single electron oxidation of enamines is a well-established activation mode for organocatalytic enantioselective α-functionalizations of simple aldehydes and ketones.[1] Due to the intrinsic limitations of enamine catalysis, the oxidation of the corresponding α-branched ketones has so far not been reported. Herein we disclose the first direct and asymmetric α-aryloxylation of cyclic ketones via enol catalysis, using quinones as the reaction partner. Catalytic amounts of a phosphoric acid promote the exclusive formation of α,α-disubstituted ketones from the corresponding α-substituted ketones in good yields and enantioselectivities (up to 96...
May 22, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29786921/room-temperature-ferroelectricity-in-an-organic-cocrystal
#2
Adam J Matzger, Ren A Wiscons, Nagula Rajesh Goud, Joshua T Damron
Ferroelectric materials exhibit switchable remanent polarization due to reversible symmetry breaking under an applied electric field. Previous research has leveraged temperature-induced neutral-ionic transitions in charge-transfer (CT) cocrystals to access ferroelectrics that operate through displacement of molecules under an applied field. However, displacive ferroelectric behavior is rare in organic CT cocrystals and achieving a Curie temperature (TC) above ambient has been elusive. Here a cocrystal between acenaphthene and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane is presented that shows switchable remanent polarization at room temperature (TC = 68°C)...
May 22, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29786915/reversible-oxidative-addition-reductive-elimination-of-si-h-bond-to-base-stabilized-silylenes-a-theoretical-insight
#3
Tsuyoshi Kato, Masayuku Nakagaki, Antoine Baceiredo, Shigeyoshi Sakaki
Although oxidative addition (O.A.) and reductive elimination (R.E.) are exceedingly important processes in organometallic chemistry, such processes are still extremely rare for main group element species. Here we report a theoretical study on the reaction of phosphine-stabilized silylenes with silanes which proceeds via reversible O.A./R.E. at room temperature. Of particular interest, this theoretical approach highlights the important role of the ligand, which can greatly affect kinetics and energy balance of the reaction...
May 22, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29786911/esipt-modulated-emission-of-lanthanide-complexes-different-energy-transfer-pathway-and-multi-responses
#4
Si-Si Sun, Zheng Wang, Xiang Wen Wu, Jian-Hua Zhang, Chao-Jie Li, Shao-Yun Yin, Ling Chen, Mei Pan, Cheng-Yong Su
Two series of isostructural lanthanide coordination complexes, namely, LIFM-42(Ln), Ln = Eu, Tb, Gd, and LIFM-43(Ln), Ln = Er, Yb) were synthesized through the self-assembly of an ESIPT (excited-state intramolecular proton transfer) ligand, H2hpi2cf (5-(2-(5-fluoro-2-hydroxyphenyl)-4,5-bis(4-fluorophenyl)-1H-imidazol-1-yl)isophthalic acid) with different lanthanide ions. In the coordination structures linked by the ligands and oxo-bridged LnIII2 clusters (for LIFM-42(Ln) series) or isolated LnIII ions (for LIFM-43(Ln) series), the ESIPT ligand can serve as both the host and antenna for protecting and sensitizing the photoluminescence (PL) of LnIII ions...
May 22, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29786906/reversible-c-h-activation-facile-b-c-b-h-metathesis-and-apparent-hydroboration-catalysis-by-a-xanthene-based-frustrated-lewis-pair
#5
Petra Vasko, Ili A Zulkifly, M Ángeles Fuentes, Zhenbo Mo, Jamie Hicks, Paul C J Kämer, Simon Aldridge
A dimethylxanthene-based phosphine/borane frustrated Lewis pair (FLP) is shown to effect reversible C-H activation, cleaving phenylacetylene, PhCCH, to give an equilibrium mixture of the free FLP and phosphonium acetylide in CD₂Cl₂ solution at room temperature. This system also reacts with B-H bonds although in a different fashion: reactions with HBpin and HBcat proceed via C-B/B-H metathesis, leading to replacement of the -B(C₆F₅)₂ Lewis acid component by -Bpin/-Bcat, and transfer of HB(C₆F₅)₂ to the phosphine Lewis base...
May 22, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29786849/isolation-and-characterization-of-wheat-derived-nonspecific-lipid-transfer-protein-2-nsltp2
#6
Sara Bosi, Jessica Fiori, Giovanni Dinelli, Neil Rigby, Emanuela Leoncini, Cecilia Prata, Valeria Bregola, Ilaria Marotti, Roberto Gotti, Marina Naldi, Luca Massaccesi, Marco Malaguti, Paul Kroon, Silvana Hrelia
Numerous studies support the protective role of bioactive peptides against cardiovascular diseases. Cereals represent the primary source of carbohydrates, but they also contain substantial amounts of proteins, therefore representing a potential dietary source of bioactive peptides with nutraceutical activities. The analysis of wheat extracts purified by chromatographic techniques by means of HPLC-UV/nanoLC-nanoESI-QTOF allowed the identification of a signal of about 7 kDa which, following data base searches, was ascribed to a nonspecific lipid-transfer protein (nsLTP) type 2 from Triticum aestivum (sequence coverage of 92%)...
May 22, 2018: Journal of Food Science
https://www.readbyqxmd.com/read/29786761/engineering-terpenoid-production-through-transient-expression-in-nicotiana-benthamiana
#7
REVIEW
James Reed, Anne Osbourn
Terpenoids are the most structurally diverse class of plant natural products with a huge range of commercial and medical applications. Exploiting this enormous potential has historically been hindered due to low levels of these compounds in their natural sources, making isolation difficult, while their structural complexity frequently makes synthetic chemistry approaches uneconomical. Engineering terpenoid biosynthesis in heterologous host production platforms provides a means to overcome these obstacles. In particular, plant-based production systems are attractive as they provide the compartmentalisation and cofactors necessary for the transfer of functional pathways from other plants...
May 21, 2018: Plant Cell Reports
https://www.readbyqxmd.com/read/29786728/selenization-of-nimn-layered-double-hydroxide-with-enhanced-electrocatalytic-activity-for-oxygen-evolution
#8
Jing Du, Zehua Zou, Ailing Yu, Cailing Xu
Exploiting highly active oxygen evolution reaction electrocatalysts is of great importance in the cost-effective generation of clean fuels. Herein, the preparation of NiMn-layered double hydroxide with selenization is adopted to reduce the charge transfer resistance of the electrocatalytic oxygen evolution reaction and enhance electrocatalytic performance. As a result, this selenization product of NiMn-layered double hydroxide can reach a current density of 10 mA cm-2 at a low overpotential of 280 mV on glassy carbon electrode in 1...
May 22, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29786719/energy-transfer-chemiluminescence-for-ratiometric-ph-imaging
#9
Weiwei An, Ralph P Mason, Alexander R Lippert
Chemiluminescence imaging offers a low background and high sensitivity approach to imaging analytes in living cells and animals. Intensity-based measurements have been developed, but require careful consideration of kinetics, probe localization, and fluctuations in quantum yield, all of which complicate quantification. Here, we report a ratiometric strategy for quantitative chemiluminescence imaging of pH. The strategy relies on an energy transfer cascade of chemiluminescence emission from a spiroadamantane 1,2-dioxetane to a ratiometric pH indicator via fluorescent dyes in Enhancer solutions...
May 22, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29786710/direct-observation-of-the-oxidation-of-dna-bases-by-phosphate-radicals-formed-under-radiation-a-model-of-the-backbone-to-base-hole-transfer
#10
Jun Ma, Jean-Louis Marignier, Pascal Pernot, Chantal Houée-Levin, Anil Kumar, Michael D Sevilla, Amitava Adhikary, Mehran Mostafavi
In irradiated DNA, by the base-to-base and backbone-to-base hole transfer processes, the hole (i.e., the unpaired spin) localizes on the most electropositive base, guanine. Phosphate radicals formed via ionization events in the DNA-backbone must play an important role in the backbone-to-base hole transfer process. However, earlier studies on irradiated hydrated DNA, on irradiated DNA-models in frozen aqueous solution and in neat dimethyl phosphate showed the formation of carbon-centered radicals and not phosphate radicals...
May 22, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29786706/hg-ii-interactions-with-t-rich-regions-in-oligonucleotides-effects-of-positional-variations-on-the-electrochemical-properties
#11
Ajar Kamal, Renu Sharma, Zhe She, Heinz-Bernhard Kraatz
Hg(ii) binding to thymine-rich oligonucleotides (ODNs) is investigated electrochemically. The focus of this study is to probe the effects of position on the electrochemical response. For this purpose, three oligonucleotides were investigated in which the position of a hexa-thymine repeat is varied within a surface-supported oligonucleotide. The hexa repeats were placed in the top, middle, and bottom positions within the strand with respect to the gold surface. The effects were monitored by electrochemical impedance spectroscopy and scanning electrochemical microscopy...
May 22, 2018: Analyst
https://www.readbyqxmd.com/read/29786667/mass-transfer-in-osmotic-dehydration-of-kiwiberry-experimental-and-mathematical-modelling-studies
#12
Michał Bialik, Artur Wiktor, Piotr Latocha, Ewa Gondek
The aim of this study was to analyze the impact of osmotic solutions and temperature on the osmotic dehydration (OD) of two cultivars of kiwiberry. OD was carried out in sucrose, xylitol and maltitol solutions at 30 °C and 50 °C, respectively. The process of osmotic dehydration was described by the means of water loss (WL), solid gain (SG), weight reduction (WR), and water content changes. Moreover, dehydration was described by mathematical models often used in the literature. The highest WL, WR and SG values were observed for samples treated by xylitol and maltitol at 50 °C...
May 22, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29786663/modeling-the-effect-of-primary-and-secondary-twinning-on-texture-evolution-during-severe-plastic-deformation-of-a-twinning-induced-plasticity-steel
#13
Laszlo S Toth, Christian Haase, Robert Allen, Rimma Lapovok, Dmitri A Molodov, Mohammed Cherkaoui, Haitham El Kadiri
Modeling the effect of deformation twinning and the ensuing twin-twin- and slip-twin-induced hardening is a long-standing problem in computational mechanical metallurgy of materials that deform by both slip and twinning. In this work, we address this effect using the twin volume transfer method, which obviates the need of any cumbersome criterion for twin variant selection. Additionally, this method is capable of capturing, at the same time, secondary or double twinning, which is particularly important for modeling in large strain regimes...
May 22, 2018: Materials
https://www.readbyqxmd.com/read/29786650/a-review-of-tunable-wavelength-selectivity-of-metamaterials-in-near-field-and-far-field-radiative-thermal-transport
#14
Yanpei Tian, Alok Ghanekar, Matt Ricci, Mikhail Hyde, Otto Gregory, Yi Zheng
Radiative thermal transport of metamaterials has begun to play a significant role in thermal science and has great engineering applications. When the key features of structures become comparable to the thermal wavelength at a particular temperature, a narrowband or wideband of wavelengths can be created or shifted in both the emission and reflection spectrum of nanoscale metamaterials. Due to the near-field effect, the phenomena of radiative wavelength selectivity become significant. These effects show strong promise for applications in thermophotovoltaic energy harvesting, nanoscale biosensing, and increased energy efficiency through radiative cooling in the near future...
May 22, 2018: Materials
https://www.readbyqxmd.com/read/29786609/comparison-of-trapped-charges-and-hysteresis-behavior-in-hbn-encapsulated-single-mos-sub-2-sub-flake-based-field-effect-transistors-on-sio-sub-2-sub-and-hbn-substrates
#15
Changhee Lee, Servin Rathi, Muhammad Atif Khan, Dongsuk Lim, Yunseob Kim, Sun Jin Yun, Doo-Hyeb Youn, Kenji Watanabe, Takashi Taniguchi, Gil-Ho Kim
Molybdenum disulfide (MoS<sub>2</sub>) based field effect transistors (FETs) are of considerable interest in electronic and opto-electronic applications but often have large hysteresis and threshold voltage instabilities. In this study, by using advanced transfer techniques, hexagonal boron nitride (hBN) encapsulated FETs based on a single, homogeneous and atomic-thin MoS<sub>2</sub> flake are fabricated on hBN and SiO<sub>2</sub> substrates...
May 22, 2018: Nanotechnology
https://www.readbyqxmd.com/read/29786518/evaluation-of-serum-ige-in-peach-allergic-patients-with-systemic-reaction-by-using-recombinant-pru-p-7-gibberellin-regulated-protein
#16
Y Mori, F Okazaki, C Inuo, Y Yamaguchi, S Masuda, S Sugiura, T Fukuie, M Nagao, I Tsuge, T Yosikawa, A Yagami, K Matsunaga, T Fujisawa, K Ito, H Narita, Y Kondo
BACKGROUND: Lipid transfer protein (LTP) is a major fruit allergen. It has, however, recently been revealed that the systemic reaction in peach-allergic patients is related not only to LTP (Pru p 3) but also to gibberellin-regulated protein (Pru p 7). We investigated recombinant Pru p 7 (rPru p 7) for its potential use in worldwide standardization for the diagnosis of peach allergy. METHODS: Natural Pru p 7 (nPru p 7) was purified from peach crude extract using a monoclonal antibody affinity column...
May 18, 2018: Allergologia et Immunopathologia
https://www.readbyqxmd.com/read/29786444/exploring-the-confinement-effect-of-carbon-nanotubes-on-the-electrochemical-properties-of-prussian-blue-nanoparticles
#17
Ti-Wei Chen, Zhong-Qiu Li, Kang Wang, Feng-Bin Wang, Xing-Hua Xia
A novel and efficient photochemical method has been proposed for the encapsulation of Prussian blue nanoparticles (PBNPs) inside the channels of carbon nanotubes (PB-in-CNTs) in an acidic ferrocyanide solution under UV/Vis illumination and the confinement effect of CNTs on the electrochemical properties of PBNPs is systematically explored. PB-in-CNTs shows a faster electron transfer process, an enhanced electrocatalytic activity toward the reduction of H2O2 and an increased anti-base ability compared to PBNPs loaded outside of CNTs (PB-out-CNTs)...
May 22, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29786431/ultrasonic-assisted-spin-coating-improved-junction-by-enhanced-permeation-of-coating-material-within-nanostructures
#18
Jong-Won Yun, Farman Ullah, Se-Jeong Jang, Do Hui Kim, Tri Khoa Nguyen, Ki Yeon Ryu, Shinuk Cho, Joon I Jang, Dooyong Lee, Sungkyun Park, Yong Soo Kim
Over the last decades, the spin coating (SC) technique has been widely used to prepare thin films of various materials in liquid phase on arbitrary substrates. The technique simply relies on centrifugal force to spread a coating solution radially outwards over the substrate. This mechanism works fairly well for solutions with low surface tension to form thin films of reasonable junctions on smooth substrates. Here, we present a modified SC technique, namely ultrasonic-assisted spin-coating (UASC), to form thin films of coating solution having high surface tension on rough substrates with excellent junctions...
May 22, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29786429/development-of-a-nanostructured-%C3%AE-mno2-carbon-paper-composite-for-removal-of-ni2-mn2-ions-by-electrosorption
#19
Pengju Li, Yang Gui, Daniel John Blackwood
Toxic metal ions, such as Ni2+ and Mn2+, in industrial waste streams are non-biodegradable and can cause damage to the human body. Electrochemical cleaning techniques are attractive as they offer more control and produce less sludge than chemical / biological approaches without the high pressures needed for membranes. Here nanoneedle structured α-MnO2/carbon fiber paper (CFP) composites were synthesized by a hydrothermal approach and used as electrodes for combined electro-adsorption and capacitive deionization removal of nickel and manganese ions from pseudo industrial waste streams...
May 22, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29786428/electrochemical-impedance-spectroscopy-for-real-time-detection-of-lipid-membrane-damage-based-on-a-porous-self-assembly-monolayer-support
#20
Meng Zhang, Qingyu Zhai, Liping Wan, Li Chen, Yu Peng, Chunyan Deng, Juan Xiang, Jiawei Yan
Layer-by-layer dissolution and permeable pore formation are two typical membrane damage pathways, which induce membrane function disorder and result in serious disease, such as Alzheimer's disease, Keshan disease, Sickle-cell disease and so on. To effectively distinguish and sensitively monitor these two typical membrane damage pathways, a facile electrochemical impedance strategy was developed on a porous self-assembly monolayer (pSAM) supported bilayer lipid membrane (BLM). The pSAM was prepared by selectively electrochemical reductive desorption of the mercaptopropionic acid in a mixed mercaptopropionic acid/11-mercaptoundecanoic acid self-assembled monolayer, which created plenty of nanopores with tens of nanometers in diameter and several nanometers in height (defined as inner-pores)...
May 22, 2018: Analytical Chemistry
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