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https://www.readbyqxmd.com/read/28088103/chemically-enzymatic-synthesis-of-photosensitive-dna
#1
Kinga Westphal, Magdalena Zdrowowicz, Agnieszka Zylicz-Stachula, Janusz Rak
The sensitizing propensity of radio-/photosensitizing nucleoside depends on DNA sequence surrounding a sensitizer. Therefore, in order to compare sensitizers with regard to their ability to induce a DNA damage one has to study the sequence dependence of damage yield. However, chemical synthesis of oligonucleotides labeled with sensitizing nucleosides is hindered due to the fact that a limited number of such nucleoside phosphoramidites are accessible. Here, we report on a chemically-enzymatic method, employing a DNA polymerase and ligase, that enables a modified nucleoside, in the form of its 5'-triphosphate, to be incorporated into DNA fragment in a pre-determined site...
January 5, 2017: Journal of Photochemistry and Photobiology. B, Biology
https://www.readbyqxmd.com/read/28080069/direct-construction-of-2-3-dihydroxy-2-3-diaryltetrahydrofurans-via-n-heterocyclic-carbene-base-mediated-domino-reactions-of-aromatic-aldehydes-and-vinyl-selenone
#2
Atanu Bhaumik, Ram Subhawan Verma, Bhoopendra Tiwari
A one-pot, stereoselective construction of 2,3-dihydroxy-2,3-diaryltetrahydrofurans has been achieved via N-heterocyclic carbene (NHC)/base-mediated domino reactions of aldehydes and vinyl selenone. The products containing two contiguous quaternary hydroxyl functionalities among the three stereocenters are obtained advantageously as either acetals or ketals through the formation of five new chemical bonds in a single operation. This report constitutes an altogether different reactivity of vinyl selenone in comparison with the corresponding sulfones and phosphonates under NHC/base-mediated reactions...
January 12, 2017: Organic Letters
https://www.readbyqxmd.com/read/28080050/altering-product-selectivity-by-mechanochemistry
#3
Jose G Hernandez, Carsten Bolm
Mechanochemical activation achieved by grinding, shearing, pulling or milling opens unique opportunities in synthetic organic chemistry. Common features are that mechanochemistry facilitates reactions with insoluble reactants, enables high-yielding solvent-free synthetic procedures and shortens reaction times, among others. However, mechanochemical techniques can also alter chemical reactivity and selectivity compared to the analogous solution-based protocols. As a consequence, solvent-free milling can lead to different product compositions or equilibration mixtures than in solution...
January 12, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28080042/relative-stability-of-empty-exohedral-fullerenes-%C3%AF-delocalization-versus-strain-and-steric-hindrance
#4
Yang Wang, Sergio Díaz-Tendero, Manuel Alcami, Fernando Martin
Predicting and understanding the relative stability of exohedral fullerenes is an important aspect of fullerene chemistry, since the experimentally formed structures do not generally follow the rules that govern addition reactions and/or the making of pristine fullerenes. First-principles theoretical calculations are of limited applicability due to the large number of possible isomeric forms, e.g., more than 50 billion for C60X8. Here we propose a simple model, exclusively based on topological arguments, that allows one to predict the relative stability of exohedral fullerenes without the need for electronic structure calculations or geometry optimizations...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28079984/medical-application-of-glycosaminoglycans-a-review
#5
REVIEW
Alexander Köwitsch, Guoying Zhou, Thomas Groth
The characteristic molecular composition of the different glycosaminoglycans (GAG) is related to their role as structural components and regulators of a multitude of functions of proteins, cells and tissues in the human body. Therefore, it is not surprising that GAG are widely used as coating materials for implants, components of 3D-constructs like tissue engineering scaffolds and hydrogels, but also as diagnostic devices like biosensors and in controlled release applications. Beside a physisorption or encapsulation of GAG, these applications often require their chemical modification to allow a stable covalent attachment on surfaces or cross-linking reactions with other molecules...
January 12, 2017: Journal of Tissue Engineering and Regenerative Medicine
https://www.readbyqxmd.com/read/28079944/an-isolable-silicon-dicarbonate-complex-from-carbon-dioxide-activation-with-a-silylone
#6
Alexander Burchert, Shenglai Yao, Robert Müller, Caspar Schattenberg, Yun Xiong, Martin Kaupp, Matthias Driess
The first isolable molecular silicon dicarbonate complex (bis-NHC)Si(CO3 )2 2 (bis-NHC=H2 C[{NC(H)=C(H)N(Dipp)}C:]2 , Dipp=2,6-iPr2 C6 H3 ) was synthesized by facile reaction of the bis-N-heterocyclic carbene stabilized silylone (bis-NHC)Si 1, bearing a zero-valent silicon atom, with carbon dioxide. The monomeric silicon dioxide complex (bis-NHC)SiO2 3 supported by the bis-NHC ligand was proposed as a key intermediate resulting from double oxygenation of the zero-valent silicon atom in 1 by two molar equivalents of CO2 under liberation of CO; its subsequent Lewis acid-base reaction with CO2 leads to 2 which has been fully characterized including an single-crystal X-ray diffraction analysis...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28079365/twist-and-shout-single-molecule-mechanochemistry
#7
Hongbin Li, Gilbert C Walker
Chemical reactions can be accelerated by various means, including applied mechanical forces. If the direction of the force does not project well onto the desired reaction coordinate, then only poor acceleration is achieved. Recent developments in single polymer mechanics illustrate how to overcome this limitation, in a simple cis-trans isomerization reaction. Generalizing the approach, synthetic chemistry can be used to attach tethers to different parts of reacting molecular fragments to direct the force usefully...
January 12, 2017: ACS Nano
https://www.readbyqxmd.com/read/28079362/intensive-study-on-catalytical-behavior-of-n-methylphenothiazine-as-a-soluble-mediator-to-oxidize-li2o2-cathode-of-li-o2-battery
#8
Ningning Feng, Xiaowei Mu, Xueping Zhang, Ping He, Haoshen Zhou
Aprotic Li-O2 batteries have attracted worldwide interest owing to their ultra-high theoretical energy density. However, the practical Li-O2 batteries still suffer from high charge overpotential and low energy efficiency resulting from the sluggish kinetics in electrochemically oxidizing the insulating lithium peroxide (Li2O2). Recently, dissolved redox mediators in the electrolyte have enabled the effective catalytic oxidation of Li2O2 at the liquid-solid interface. Here, we report that the incorporation of N-methylphenothiazine (MPT), as a redox shuttle in Li-O2 batteries, provides a dramatic reduction in charge overpotential to 0...
January 12, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28079307/coordination-of-krf2-to-a-naked-metal-cation-mg-2
#9
Matic Lozinšek, Hélène P A Mercier, David S Brock, Boris Žemva, Gary J Schrobilgen
Examples of coordination compounds in which KrF2 functions as a ligand are very rare. In contrast, XeF2 provides a rich coordination chemistry with a variety of main-group and transition metal cations. The reactions of Mg(AsF6 )2 and KrF2 in HF or BrF5 solvent have afforded [Mg(KrF2 )4 (AsF6 )2 ] and [Mg(KrF2 )4 (AsF6 )2 ]⋅2 BrF5 , respectively, the first examples of a metal cation ligated by KrF2 . Their X-ray crystal structures and Raman spectra show that the KrF2 ligands and [AsF6 ](-) anions are F-coordinated to a naked Mg(2+) cation...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28079290/clamped-hybridization-chain-reactions-for-the-self-assembly-of-patterned-dna-hydrogels
#10
Jianbang Wang, Jie Chao, Huajie Liu, Shao Su, Lianhui Wang, Wei Huang, Itamar Willner, Chunhai Fan
DNA hydrogels hold great potential for biological and biomedical applications owing to their programmable nature and macroscopic sizes. However, most previous studies involve spontaneous and homogenous gelation procedures in solution, which often lack precise control. A clamped hybridization chain reaction (C-HCR)-based strategy has been developed to guide DNA self-assembly to form macroscopic hydrogels. Analogous to catalysts in chemical synthesis or seeds in crystal growth, we introduced DNA initiators to induce the gelation process, including crosslinked self-assembly and clamped hybridization in three dimensions with spatial and temporal control...
January 12, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28079220/facile-pentagon-formation-in-the-dissociation-of-polyaromatics
#11
Arjen J de Haas, Jos Oomens, Jordy Bouwman
Energetic processing of gaseous polycyclic aromatic hydrocarbons (PAHs) plays a pivotal role in the chemistries of inter- and circumstellar environments, certain planetary atmospheres, and also in the chemistry of combustion and soot formation. Although the precursor PAH species have been extensively characterized, the products from these gaseous breakdown reactions have received far less attention. It has been particularly challenging to accurately determine their molecular structure in gas-phase experiments, where comparisons against theoretical modeling are best made...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28079211/electrolyte-controlled-discharge-product-distribution-of-na-o2-batteries-a-combined-computational-and-experimental-study
#12
Beizhou Wang, Ning Zhao, Youwei Wang, Wenqing Zhang, Wencong Lu, Xiangxin Guo, Jianjun Liu
Tuning the composition of discharge products is an important strategy to reduce charge potential, suppress side reactions, and improve the reversibility of metal-oxygen batteries. In the present study, first-principles calculations and experimental confirmation were performed to unravel the influence of O2 pressure, particle size, and electrolyte on the composition of charge products in Na-O2 batteries. The electrolytes with medium and high donor numbers (>12.5) are favorable for the formation of sole NaO2, while those with low donor numbers (<12...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28079151/discovery-and-mechanistic-characterization-of-selective-inhibitors-of-h2s-producing-enzyme-3-mercaptopyruvate-sulfurtransferase-3mst-targeting-active-site-cysteine-persulfide
#13
Kenjiro Hanaoka, Kiyoshi Sasakura, Yusuke Suwanai, Sachiko Toma-Fukai, Kazuhito Shimamoto, Yoko Takano, Norihiro Shibuya, Takuya Terai, Toru Komatsu, Tasuku Ueno, Yuki Ogasawara, Yukihiro Tsuchiya, Yasuo Watanabe, Hideo Kimura, Chao Wang, Masanobu Uchiyama, Hirotatsu Kojima, Takayoshi Okabe, Yasuteru Urano, Toshiyuki Shimizu, Tetsuo Nagano
Very recent studies indicate that sulfur atoms with oxidation state 0 or -1, called sulfane sulfurs, are the actual mediators of some physiological processes previously considered to be regulated by hydrogen sulfide (H2S). 3-Mercaptopyruvate sulfurtransferase (3MST), one of three H2S-producing enzymes, was also recently shown to produce sulfane sulfur (H2Sn). Here, we report the discovery of several potent 3MST inhibitors by means of high-throughput screening (HTS) of a large chemical library (174,118 compounds) with our H2S-selective fluorescent probe, HSip-1...
January 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28078726/dissecting-the-cytochrome-p450-1a2-and-3a4-mediated-metabolism-of-aflatoxin-b1-in-ligand-and-protein-contributions
#14
Lars Olsen, Flemming S Jørgensen, Silvia Bonomo
Aflatoxin B1 (AFB1) is a chemically intriguing compound because it has several potential sites of metabolism (SOMs) while only some of them are observed experimentally. Cytochrome P450 (CYP) 3A4 and 1A2 are the major isoforms involved in its metabolism. Here, we systematically investigate reactivity and accessibility of all possible SOMs in these two CYPs to elucidate AFB1 metabolism. Density functional theory (DFT) calculations were used to determine activation energies for each possible reaction. Aliphatic hydroxylation on position 9A and 3α are energetically favored, whereas position 9 is the preferred site for epoxidation...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078718/fabric-based-alkaline-direct-formate-microfluidic-fuel-cells
#15
Kryls Domalaon, Catherine Tang, Alex Mendez, Franky Bernal, Krutarth Purohit, Linda Pham, John Haan, Frank A Gomez
Fabric-based microfluidic fuel cells (MFCs) serve as a novel, cost-efficient alternative to traditional FCs and batteries, since fluids naturally travel across fabric via capillary action, eliminating the need for an external pump and lowering production and operation costs. Building on previous research with Y-shaped paper-based MFCs, fabric-based MFCs mitigate fragility and durability issues caused by long periods of fuel immersion. In the present work we describe a microfluidic fabric-based direct formate fuel cell (DFFC), with 5 M potassium formate and 30% hydrogen peroxide as the anode fuel and cathode oxidant, respectively...
January 12, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28078627/nanostructured-materials-synthesis-using-ultrasound
#16
REVIEW
Jordan J Hinman, Kenneth S Suslick
Recent applications of ultrasound to the production of nanostructured materials are reviewed. Sonochemistry permits the production of novel materials or provides a route to known materials without the need for high bulk temperatures, pressures, or long reaction times. Both chemical and physical phenomena associated with high-intensity ultrasound are responsible for the production or modification of nanomaterials. Most notable are the consequences of acoustic cavitation: the formation, growth, and implosive collapse of bubbles, and can be categorized as primary sonochemistry (gas-phase chemistry occurring inside collapsing bubbles), secondary sonochemistry (solution-phase chemistry occurring outside the bubbles), and physical modifications (caused by high-speed jets, shockwaves, or inter-particle collisions in slurries)...
February 2017: Topics in Current Chemistry (Journal)
https://www.readbyqxmd.com/read/28078551/the-proteolysis-adaptor-nbla-binds-to-the-n-terminus-of-%C3%AE-phycocyanin-implications-for-the-mechanism-of-phycobilisome-degradation
#17
Amelia Y Nguyen, William P Bricker, Hao Zhang, Daniel A Weisz, Michael L Gross, Himadri B Pakrasi
Phycobilisome (PBS) complexes are massive light-harvesting apparati in cyanobacteria that capture and funnel light energy to the photosystem. PBS complexes are dynamically degraded during nutrient deprivation, which causes severe chlorosis, and resynthesized during nutrient repletion. PBS degradation occurs rapidly after nutrient step down, and is specifically triggered by non-bleaching protein A (NblA), a small proteolysis adaptor that facilitates interactions between a Clp chaperone and phycobiliproteins...
January 11, 2017: Photosynthesis Research
https://www.readbyqxmd.com/read/28077884/chemical-vs-physical-acceleration-of-cement-hydration
#18
Dale P Bentz, Franco Zunino, Didier Lootens
Cold weather concreting often requires the use of chemical accelerators to speed up the hydration reactions of the cement, so that setting and early-age strength development will occur in a timely manner. While calcium chloride (dihydrate - CaCl2·2H2O) is the most commonly used chemical accelerator, recent research using fine limestone powders has indicated their high proficiency for physically accelerating early-age hydration and reducing setting times. This paper presents a comparative study of the efficiency of these two approaches in accelerating hydration (as assessed via isothermal calorimetry), reducing setting times (Vicat needle), and increasing early-age mortar cube strength (1 d and 7 d)...
November 2016: Concr Int
https://www.readbyqxmd.com/read/28075563/particulate-formation-from-a-copper-oxide-based-oxygen-carrier-in-chemical-looping-combustion-for-co2-capture
#19
Feng He, William Patrick Linak, Shuang Deng, Fanxing Li
Attrition behavior and particle loss of a copper oxide-based oxygen carrier from a methane chemical looping combustion (CLC) process was investigated in a fluidized bed reactor. The aerodynamic diameters of most elutriated particulates, after passing through a horizontal settling duct, range between 2 and 5 μm. A notable number of submicron particulates are also identified. Oxygen carrier attrition was observed to lead to increased CuO loss resulting from the chemical looping reactions, i.e., Cu is enriched in small particles generated primarily from fragmentation in the size range of 10-75 μm...
January 11, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28075562/evidence-for-a-di-%C3%A2%C2%B5-oxo-diamond-core-in-the-mn-iv-fe-iv-activation-intermediate-of-ribonucleotide-reductase-from-chlamydia-trachomatis
#20
Ryan J Martinie, Elizabeth J Blaesi, Carsten Krebs, J Martin Bollinger, Alexey Silakov, Christopher J Pollock
High-valent iron and manganese complexes effect some of the most challenging biochemical reactions known, including hydrocarbon and water oxidations associated with the global carbon cycle and oxygenic photosynthesis, respectively. Their extreme reactivity presents an impediment to structural characterization, but their biological importance and potential chemical utility have, nevertheless, motivated extensive efforts toward that end. Several such intermediates accumulate during activation of class I ribonucleotide reductase (RNR) β subunits, which self-assemble dimetal cofactors with stable one-electron oxidants that serve to initiate the enzyme's free-radical mechanism...
January 11, 2017: Journal of the American Chemical Society
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