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https://www.readbyqxmd.com/read/29667837/oxazaborinines-from-vinylogous-n-allylic-amides-reactivities-of-underexplored-heterocyclic-building-blocks
#1
Cedric L Hugelshofer, Vignesh Palani, Richmond Sarpong
Access to a new class of oxazaborinines using an efficient transition-metal-catalyzed rearrangement is demonstrated. The method overcomes the synthetic challenge of achieving an aza-Claisen rearrangement of vinylogous N-allylic amide substrates, giving rise to a variety of highly modifiable oxazaborinine products. An investigation of the unique reactivity of these boron-based heterocycles has unveiled their underexplored potential as valuable building blocks and intermediates for organic synthesis.
April 18, 2018: Organic Letters
https://www.readbyqxmd.com/read/29667831/a-rigorous-method-of-calculating-exfoliation-energies-from-first-principles
#2
Jong Hyun Jung, Cheol-Hwan Park, Jisoon Ihm
The exfoliation energy, the energy required to peel off an atomic layer from the surface of a bulk material, is of fundamental importance in the science and engineering of two-dimensional materials. Traditionally, the exfoliation energy of a material has been obtained from first-principles by calculating the difference in the ground-state energy between (i) a slab of N atomic layers ( N ≫ 1) and (ii) a slab of N - 1 atomic layers plus an atomic layer separated from the slab. In this paper, we prove that the exfoliation energy can be obtained exactly as the difference in the ground-state energy between a bulk material (per atomic layer) and a single isolated layer...
April 18, 2018: Nano Letters
https://www.readbyqxmd.com/read/29666867/investigation-of-ternary-metal-dodecaborides-m-1-m-2-m-3-b-12-m-1-m-2-and-m-3-zr-y-hf-and-gd
#3
Georgiy Akopov, Inwhan Roh, Zachary C Sobell, Michael T Yeung, Richard B Kaner
Samples of metal borides with a nominal composition of ((M1)(1-x-z)(M2)(x)(M3)(z)) : 20B (M1, M2 and M3 = Zr, Y, Hf and Gd) were prepared by arc-melting and studied for phase composition (using powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS)) and mechanical properties (Vickers hardness). Ternary metal dodecaboride phases were successfully synthesized for the majority of compositions, including stabilization of two high-pressure (6.5 GPa) phases (cubic-UB12 structure), HfB12 and GdB12, in (Zr1-x-zHfxGdz) : 20B and (Y1-x-zHfxGdz) : 20B nominal alloy compositions...
April 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29665269/highly-fluorescent-magnetic-nanobeads-with-a-remarkable-stokes-shift-as-labels-for-enhanced-detection-in-immunoassays
#4
Francesca Salis, Ana B Descalzo, Elena Benito-Peña, María C Moreno-Bondi, Guillermo Orellana
Fluorescence immunoassays are popular for achieving high sensitivity, but they display limitations in biological samples due to strong absorption of light, background fluorescence from matrix components, or light scattering by the biomacromolecules. A powerful strategy to overcome these problems is introduced here by using fluorescent magnetic nanobeads doped with two boron-dipyrromethane dyes displaying intense emission in the visible and near-infrared regions, respectively. Careful matching of the emission and absorption features of the dopants leads to a virtual Stokes shift larger than 150 nm achieved by an intraparticle Förster resonance energy transfer (FRET) process between the donor and the acceptor dyes...
April 17, 2018: Small
https://www.readbyqxmd.com/read/29665265/nitrogen-fluorine-and-boron-ternary-doped-carbon-fibers-as-cathode-electrocatalysts-for-zinc-air-batteries
#5
Lei Wang, Yueqing Wang, Mingguang Wu, Zengxi Wei, Chunyu Cui, Minglei Mao, Jintao Zhang, Xiaopeng Han, Quanhui Liu, Jianmin Ma
Zinc-air batteries with high-density energy are promising energy storage devices for the next generation of energy storage technologies. However, the battery performance is highly dependent on the efficiency of oxygen electrocatalyst in the air electrode. Herein, the N, F, and B ternary doped carbon fibers (TD-CFs) are prepared and exhibited higher catalytic properties via the efficient 4e- transfer mechanism for oxygen reduction in comparison with the single nitrogen doped CFs. More importantly, the primary and rechargeable Zn-air batteries using TD-CFs as air-cathode catalysts are constructed...
April 17, 2018: Small
https://www.readbyqxmd.com/read/29665232/glucose-responsive-trehalose-hydrogel-for-insulin-stabilization-and-delivery
#6
Juneyoung Lee, Jeong Hoon Ko, Kathryn M Mansfield, Peter C Nauka, Erhan Bat, Heather D Maynard
Effective delivery of therapeutic proteins is important for many biomedical applications. Yet, the stabilization of proteins during delivery and long-term storage remains a significant challenge. Herein, a trehalose-based hydrogel is reported that stabilizes insulin to elevated temperatures prior to glucose-triggered release. The hydrogel is synthesized using a polymer with trehalose side chains and a phenylboronic acid end-functionalized 8-arm poly(ethylene glycol) (PEG). The hydroxyls of the trehalose side chains form boronate ester linkages with the PEG boronic acid cross-linker to yield hydrogels without any further modification of the original trehalose polymer...
April 17, 2018: Macromolecular Bioscience
https://www.readbyqxmd.com/read/29665113/switchable-synthesis-of-z-homoallylic-boronates-and-e-allylic-boronates-by-enantioselective-copper-catalyzed-1-6-boration
#7
Yunfei Luo, Steven M Wales, Stamatis E Korkis, Iain D Roy, William Lewis, Hon Wai Lam
The enantioselective Cu-catalyzed 1,6-boration of (E,E)-α,β,γ,δ-unsaturated ketones is described, which gives homoallylic boronates with high enantiomeric purity and unexpectedly high Z-selectivity. By changing the solvent, the outcome can be altered to give E-allylic boronates.
April 17, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29664635/ultrafast-through-space-electronic-energy-transfer-in-molecular-dyads-built-around-dynamic-spacer-units
#8
Raymond Ziessel, Patrycja Stachelek, Anthony Harriman, Gordon J Hedley, Thomas J Roland, Arvydas Ruseckas, Ifor David William Samuel
A pair of complimentary molecular dyads have been synthesized around a 1,2-diaminocyclohexyl spacer that itself undergoes ring inversion. Despite these conformational exchange processes, the donor and acceptor occupy quite restricted spatial regions and they are not interchangeable. The donor and acceptor pair comprise disparate boron dipyrromethene dyes selected to display favorable electronic energy transfer (EET). Steady-state emission spectroscopy con-firms that through-space EET from donor to acceptor is almost quantitative, aided by the relatively short separations...
April 17, 2018: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29662988/polyvinyl-alcohol-boronate-gel-for-sodium-hydroxide-extraction
#9
Gretchen Marie Peters, Xiaodong Chi, Chandler Brockman, Jonathan L Sessler
Gels formed from commercially available polyvinyl alcohol (PVA) and 1,4-benzene diboronic acid (BdBA) in DMSO absorb NaOH efficiently from a bulk aqueous solution decreasing its pH.
April 17, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29662211/synthesis-structure-and-reaction-chemistry-of-a-nucleophilic-aluminyl-anion
#10
Jamie Hicks, Petra Vasko, Jose M Goicoechea, Simon Aldridge
The reactivity of aluminium compounds is dominated by their electron deficiency and consequent electrophilicity; these compounds are archetypal Lewis acids (electron-pair acceptors). The main industrial roles of aluminium, and classical methods of synthesizing aluminium-element bonds (for example, hydroalumination and metathesis), draw on the electron deficiency of species of the type AlR3 and AlCl3 1,2 . Whereas aluminates, [AlR4 ]- , are well known, the idea of reversing polarity and using an aluminium reagent as the nucleophilic partner in bond-forming substitution reactions is unprecedented, owing to the fact that low-valent aluminium anions analogous to nitrogen-, carbon- and boron-centred reagents of the types [NX2 ]- , [CX3 ]- and [BX2 ]- are unknown3-5 ...
April 16, 2018: Nature
https://www.readbyqxmd.com/read/29662038/alignment-of-boron-nitride-nanofibers-in-epoxy-composite-films-for-thermal-conductivity-and-dielectric-breakdown-strength-improvement
#11
Zhengdong Wang, Jingya Liu, Yonghong Cheng, Siyu Chen, Mengmeng Yang, Jialiang Huang, Hongkang Wang, Guanglei Wu, Hongjing Wu
Development of polymer-based composites with simultaneously high thermal conductivity and breakdown strength has attracted considerable attention owing to their important applications in both electronic and electric industries. In this work, boron nitride (BN) nanofibers (BNNF) are successfully prepared as fillers, which are used for epoxy composites. In addition, the BNNF in epoxy composites are aligned by using a film casting method. The composites show enhanced thermal conductivity and dielectric breakdown strength...
April 15, 2018: Nanomaterials
https://www.readbyqxmd.com/read/29660876/copper-oxide-nanoparticles-and-bulk-copper-oxide-combined-with-indole-3-acetic-acid-alter-aluminum-boron-and-iron-in-pisum-sativum-seeds
#12
Loren Ochoa, Nubia Zuverza-Mena, Illya A Medina-Velo, Juan Pedro Flores-Margez, José R Peralta-Videa, Jorge L Gardea-Torresdey
The interaction of CuO nanoparticles (nCuO), a potential nanopesticide, with the growth hormone indole-3-acetic acid (IAA) is not well understood. This study aimed to evaluate the nutritional components in seeds of green pea (Pisum sativum) cultivated in soil amended with nCuO at 50 or 100mgkg-1 , with/without IAA at 10 or 100μM. Similar treatments including bulk CuO (bCuO) and CuCl2 were set as controls. Bulk CuO at 50mgkg-1 reduced seed yield (52%), compared with control. Bulk CuO at 50mgkg-1 and nCuO at 100mgkg-1 , plus IAA at 100μM, increased iron in seeds (41 and 42%, respectively), while nCuO at 50mgkg-1 , plus IAA at 100μM reduced boron (80%, respect to control and 63%, respect to IAA at 100μM)...
April 12, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/29660503/high-circulatory-leptin-mediated-nox-2-peroxynitrite-mir21-axis-activate-mesangial-cells-and-promotes-renal-inflammatory-pathology-in-nonalcoholic-fatty-liver-disease
#13
Firas Alhasson, Ratanesh Kumar Seth, Sutapa Sarkar, Diana A Kimono, Muayad S Albadrani, Diptadip Dattaroy, Varun Chandrashekaran, Geoffrey I Scott, Samir Raychoudhury, Mitzi Nagarkatti, Prakash Nagarkatti, Anna Mae Diehl, Saurabh Chatterjee
High circulatory insulin and leptin followed by underlying inflammation are often ascribed to the ectopic manifestations in non-alcoholic fatty liver disease (NAFLD) but the exact molecular pathways remain unclear. We have shown previously that CYP2E1-mediated oxidative stress and circulating leptin in NAFLD is associated with renal disease severity. Extending the studies, we hypothesized that high circulatory leptin in NAFLD causes renal mesangial cell activation and tubular inflammation via a NOX2 dependent pathway that upregulates proinflammatory miR21...
April 7, 2018: Redox Biology
https://www.readbyqxmd.com/read/29659262/fluorescent-bodipy-anionic-boron-cluster-conjugates-as-potential-agents-for-cell-tracking
#14
Mahdi Chaari, Nerea Gaztelumendi, Justo Cabrera-González, Paula Peixoto-Moledo, Clara Viñas, Elba Xochitiotzi-Flores, Norberto Farfan, Abdelhamid Ben Salah, Carme Nogues, Rosario Nuñez
A series of novel fluorescent BODIPY-anionic boron cluster conjugates bearing [B12H12]2- (5, 6), [3,3'-Co(1,2-C2B9H11)2]- (7, 8), and [3,3'-Fe(1,2-C2B9H11)2]- (9) anions have been readily synthesized from meso-(4-hydroxyphenyl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY 4), and their structure and photoluminescence properties have been assessed. Linking anionic boron clusters to the BODIPY (4) does not alter significantly the luminescent properties of the final fluorophores, showing all of them similar emission fluorescent quantum yields (3-6%)...
April 16, 2018: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/29658890/optical-absorption-by-indirect-excitons-in-a-transition-metal-dichalcogenide-hexagonal-boron-nitride-heterostructure
#15
Matthew Nicolas Brunetti, Oleg L Berman, Roman Ya Kezerashvili
We study optical transitions in indirect excitons in transition metal dichalcogenide (TMDC) double layers separated by an integer number of hexagonal boron nitride (h-BN) monolayers. By solving the Schrödinger equation with the Keldysh potential for an indirect exciton, we obtain eigenfunctions and eigenenergies for the ground and excited states and study their dependence on the interlayer separation, controlled by varying the number of h-BN monolayers. The oscillator strength, optical absorption coefficient, and optical absorption factor, the fraction of incoming photons absorbed in the double layer, are evaluated and studied as a function of the interlayer separation...
April 16, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29658543/rosamine-with-pyronine-pyridinium-skeleton-unique-mitochondrial-targetable-structure-for-fluorescent-probes
#16
Ling Yang, Jin-Yun Niu, Ru Sun, Yu-Jie Xu, Jian-Feng Ge
Two rosamine-based probes (1a-b) with pyronine-pyridinium skeleton were designed and prepared. Probe 1a bearing boron ester unit was oxidized and eliminated upon addition of hydrogen peroxide (H2O2), and the emission spectrum exhibited OFF-ON response accompanied by 33-fold fluorescent enhancement. In contrast, the fluorescence intensity of probe 1b enhanced 58 times after the dinitrophenyl ether part within the probe was removed by nucleophilic substitution with hydrosulfide (H2S). The design concept was based on the d-PET process in pyronine-pyridinium structures, and free 4-pyridinyl-substituted pyronine dye showing strong fluorescence was released followed by elimination...
April 16, 2018: Analyst
https://www.readbyqxmd.com/read/29656475/hydrogenation-of-multiple-bonds-by-geminal-aminoborane-based-frustrated-lewis-pairs
#17
Diana Yepes, Pablo Jaque, Israel Fernandez
By means of Density Functional Theory calculations, the hydrogenation reaction of multiple bonds mediated by geminal aminoborane-based frustrated Lewis pairs (FLPs) has been explored. It is found that the release of the activated dihydrogen occurs in a concerted, yet highly asynchronous, manner. The physical factors controlling the transformation are quantitatively described in detail by means of the Activation Strain Model of reactivity in combination with the Energy Decomposition Analysis method. This approach suggests a cooperative double hydrogen transfer mechanism which is initiated by the migration of the protic (N)H and followed by the nucleophilic attack of the hydride (B)H to the carbon atom of the multiple bond...
April 14, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29655983/catalytic-asymmetric-synthesis-of-%C3%AE-methyl-p-boronophenylalanine
#18
Shingo Harada, Ryota Kajihara, Risa Muramoto, Promsuk Jutabha, Naohiko Anzai, Tetsuhiro Nemoto
p-Boronophenylalanine (l-BPA) is applied in clinical settings as a boron carrier for boron neutron capture therapy (BNCT) to cure malignant melanomas. Structural modification or derivatization of l-BPA, however, to improve its uptake efficiency into tumor cells has scarcely been investigated. We successfully synthesized (S)-2-amino-3-(4-boronophenyl)-2-methylpropanoic acid in enantioenriched form as a novel candidate molecule for BNCT. Key steps to enhance the efficiency of this synthesis were enantioselective alkylation of N-protected alanine tert-butyl ester with a Maruoka catalyst and Miyaura borylation reaction to install the boron functionality...
March 28, 2018: Bioorganic & Medicinal Chemistry Letters
https://www.readbyqxmd.com/read/29653373/combined-effect-of-salt-and-drought-on-boron-toxicity-in-puccinellia-tenuiflora
#19
Chunguang Liu, Zheng Dai, Jingye Xia, Can Chang, Hongwen Sun
Boron toxicity is a worldwide problem, usually accompanied by salt (NaCl) and drought. The combined stresses may induce complex toxicity to the plant. The aim of the present study was to investigate how the combined stresses of salt and drought affect B toxicity in plants. Puccinellia tenuiflora seedlings were planted in vermiculite. A three (B) × three (salt) × three (drought) factorial experiment (for a total of 27 treatments) was conducted. After a 30-day cultivation, plants were harvested to determine dry weight and the concentrations of B, Na+ , K+ , Ca2+ , and Mg2+ ...
April 10, 2018: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/29653052/resolving-the-chemically-discrete-structure-of-synthetic-borophene-polymorphs
#20
Gavin P Campbell, Andrew Jacob Mannix, Jonathan D Emery, Tien-Lin Lee, Nathan P Guisinger, Mark C Hersam, Michael J Bedzyk
Atomically thin two-dimensional (2D) materials exhibit superlative properties dictated by their intralayer atomic structure, which is typically derived from a limited number of thermodynamically stable bulk layered crystals (e.g., graphene from graphite). The growth of entirely synthetic 2D crystals - those with no corresponding bulk allotrope - would circumvent this dependence upon bulk thermodynamics and substantially expand the phase space available for structure-property engineering of 2D materials. However, it remains unclear if synthetic 2D materials can exist as structurally and chemically distinct layers anchored by van der Waals (vdW) forces, as opposed to strongly bound adlayers...
April 13, 2018: Nano Letters
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