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Chemical reactions

Sandeep Yadav, Ekta Sangtani, Diksha Dhawan, Rajesh G Gonnade, Debashree Ghosh, Sakya S Sen
Usually, when a silylene reacts with a transition metal Lewis acid, it forms an adduct which could be either monomeric or dimeric. However, we present here that a silylene, [PhC(NtBu)2SiN(SiMe3)2] can form both monomeric [PhC(NtBu)2Si{N(SiMe3)2} → ZnI2]·THF (1) and dimeric [{PhC(NtBu)2}(N(SiMe3)2)SiZnI,(μ-I)]2 (2) adducts upon reaction with ZnI2. The formation of 1 and 2 relies upon the solvent used for the reaction or crystallization. When the crystallization is carried out in THF complex 1 is formed, however, when the reaction and crystallization are performed in acetonitrile complex 2 is obtained...
August 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Markus A Keller, Domen Kampjut, Stuart A Harrison, Markus Ralser
The evolutionary origins of the Krebs cycle (tricarboxylic acid cycle) are not currently clear. Despite the existence of a simple non-enzymatic Krebs cycle catalyst being dismissed only a few years ago as 'an appeal to magic', citrate and other intermediates have since been discovered on a carbonaceous meteorite and do interconvert non-enzymatically. To identify a metabolism-like non-enzymatic Krebs cycle catalyst, we used combinatorial, quantitative high-throughput metabolomics to systematically screen iron and sulfate compounds in a reaction mixture that orients on the typical components of Archaean sediment...
March 13, 2017: Nature ecology & evolution
Norio Kitadai, Kumiko Nishiuchi, Akari Nishii, Keisuke Fukushi
It has long been suggested that mineral surfaces played a crucial role in the abiotic polymerization of amino acids that preceded the origin of life. Nevertheless, it remains unclear where the prebiotic process took place on the primitive Earth, because the amino acid-mineral interaction and its dependence on environmental conditions have yet to be understood adequately. Here we examined experimentally the adsorption of L-lysine (Lys) and its dimer (LysLys) on amorphous silica over a wide range of pH, ionic strength, adsorbate concentration, and the solid/water ratio, and determined the reaction stoichiometries and the equilibrium constants based on the extended triple-layer model (ETLM)...
August 15, 2017: Origins of Life and Evolution of the Biosphere
Pascal Baumann, Marie-Therese Schermeyer, Hannah Burghardt, Cathrin Dürr, Jonas Gärtner, Jürgen Hubbuch
Solution stability attributes are one of the key parameters within the production and launching phase of new biopharmaceuticals. Instabilities of active biological compounds can reduce the yield of biopharmaceutical productions, and may induce undesired reactions in patients, such as immunogenic rejections. Protein solution stability thus needs to be engineered and monitored throughout production and storage. In contrast to the gold standard of long-term storage experiments applied in industry, novel experimental and in silico molecular dynamics tools for predicting protein solution stability can be applied within several minutes or hours...
August 12, 2017: International Journal of Pharmaceutics
Torstein Kige Rye, David Fuchs, Stig Pedersen-Bjergaard, Nickolaj Jacob Petersen
A triple-flow electromembrane extraction (EME) probe was developed and coupled directly to electrospray-ionization mass spectrometry (ESI-MS). Metabolic reaction mixtures (pH 7.4) containing drug substances and related metabolites were continuously drawn (20 μL/min) into the EME probe in one flow channel, and mixed inside the probe with 7.5 μL min(-1) of 1 M formic acid as make-up flow from a second flow channel. Following this acidification, the drug substances and their related metabolites were continuously extracted by EME at 400 V, across a supported liquid membrane (SLM) comprising 2-nitrophenyl octyl ether (and for some experiments containing 30% triphenyl phosphate (TPP)), and into 20 μL min(-1) of formic acid as acceptor phase, which was introduced through a third flow channel...
August 29, 2017: Analytica Chimica Acta
Chia-Chieh Lin, Wei-Yu Chen, Hiroyuki Matsui, Niann-Shiah Wang
We measured the rates of abstraction of a hydrogen atom from specific sites in propane C3H8, 2-methyl propane (i-C4H10), and butane (n-C4H10); the sites are a primary hydrogen of C3H8 and i-C4H10 and a secondary hydrogen of n-C4H10. The excellent reproducibility of conditions of a diaphragm-less shock tube enabled us to conduct comparative measurements of the evolution of H atoms in three mixtures-(i) 0.5 ppm C2H5I + Ar, (ii) 0.5 ppm C2H5I + 50-100 ppm alkane as C3H8 or i-C4H10 or n-C4H10 + Ar, and (iii) the same concentrations of alkane + Ar without C2H5I-in the temperature range 1000-1200 K and at a pressure of 2...
August 14, 2017: Journal of Chemical Physics
Andrej Junginger, Lennart Duvenbeck, Matthias Feldmaier, Jörg Main, Günter Wunner, Rigoberto Hernandez
In chemical or physical reaction dynamics, it is essential to distinguish precisely between reactants and products for all times. This task is especially demanding in time-dependent or driven systems because therein the dividing surface (DS) between these states often exhibits a nontrivial time-dependence. The so-called transition state (TS) trajectory has been seen to define a DS which is free of recrossings in a large number of one-dimensional reactions across time-dependent barriers and thus, allows one to determine exact reaction rates...
August 14, 2017: Journal of Chemical Physics
Peter H Colberg, Raymond Kapral
The collective behavior of chemically propelled sphere-dimer motors made from linked catalytic and noncatalytic spheres in a quasi-two-dimensional confined geometry is studied using a coarse-grained microscopic dynamical model. Chemical reactions at the catalytic spheres that convert fuel to product generate forces that couple to solvent degrees of freedom as a consequence of momentum conservation in the microscopic dynamics. The collective behavior of the many-body system is influenced by direct intermolecular interactions among the motors, chemotactic effects due to chemical gradients, hydrodynamic coupling, and thermal noise...
August 14, 2017: Journal of Chemical Physics
Wenjin Cao, Dilrukshi Hewage, Dong-Sheng Yang
La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C4H4) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C4H4) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals...
August 14, 2017: Journal of Chemical Physics
Guojie Zhang, Marcus Müller
Membrane fission is a fundamental process in cells, involved inter alia in endocytosis, intracellular trafficking, and virus infection. Its underlying molecular mechanism, however, is only incompletely understood. Recently, experiments and computer simulation studies have revealed that dynamin-mediated membrane fission is a two-step process that proceeds via a metastable hemi-fission intermediate (or wormlike micelle) formed by dynamin's constriction. Importantly, this hemi-fission intermediate is remarkably metastable, i...
August 14, 2017: Journal of Chemical Physics
Chloe E Bonamici, Richard L Hervig, William S Kinman
Compositional analysis of post-detonation fallout is a tool for forensic identification of nuclear devices. However, the relationship between device composition and fallout composition is difficult to interpret because of the complex combination of physical mixing, nuclear reactions, and chemical fractionations that occur in the chaotic nuclear fireball. Using a combination of in situ microanalytical techniques - electron microprobe analysis and secondary ion mass spectrometry - we show that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd, Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test, Trinity, are reliable chemical proxies for radionuclides generated during the explosion...
August 16, 2017: Analytical Chemistry
Federico A Soria, Weiwei Zhang, Adri C T van Duin, Eduardo Martin Patrito
We used the ReaxFF reactive molecular dynamics simulations to investigate the chemical mechanisms and kinetics of thermal decomposition processes of silicon surfaces grafted with different organic molecules via Si-C bonds at atomistic level. In this work, we considered the Si(111) surface grafted with n-alkyl (ethyl, propyl, pentyl and decyl) layers in 50 % coverage and Si-CH3, Si-CCCH3 and Si-CHCHCH3 layers in full coverage. Si radicals primarily formed by the homolytic cleavage of Si-C bonds play a key role in the dehydrogenation processes that lead to the decomposition of the monolayers...
August 16, 2017: ACS Applied Materials & Interfaces
Jian Zhang, Lei Liu, Yuanyuan Wang, Yong Ren, Xin Wang, Zongbo Shi, Daizhou Zhang, Huizheng Che, Hujia Zhao, Yanfei Liu, Hongya Niu, Jianmin Chen, Xiaoye Zhang, A P Lingaswamy, Zifa Wang, Weijun Li
The characteristics of aerosol particles have been poorly evaluated even though haze episodes frequently occur in winter in Northeast China. OC/EC analysis, ion chromatography, and transmission electron microscopy (TEM) were used to investigate the organic carbon (OC) and elemental carbon (EC), and soluble ions in PM2.5 and the mixing state of individual particles during a severe wintertime haze episode in Northeast China. The organic matter (OM), NH4(+), SO4(2-), and NO3(-) concentrations in PM2.5 were 89...
August 12, 2017: Environmental Pollution
Asraa Ziadi, Naoyuki Uchida, Hiroe Kato, Rina Hisamatsu, Ayato Sato, Shinya Hagihara, Kenichiro Itami, Keiko U Torii
The increasing climate changes and global warming are leading to colossal agricultural problems such as abatement of food production and quality. As stomatal development is considered to play a key role in crop plant productivity and water-use efficiency, studying stomatal development is useful for understanding the productivity of plant systems for both natural and agricultural systems. Herein, we report the first-in-class synthetic small molecules enhancing the number of stomata in Arabidopsis thaliana that have been discovered by screening of the chemical library and further optimized by the Pd-catalyzed C-H arylation reaction...
August 15, 2017: Chemical Communications: Chem Comm
Valérie Voorsluijs, Ioannis G Kevrekidis, Yannick De Decker
The photosensitive Belousov-Zhabotinsky (pBZ) reaction has been used extensively to study the properties of chemical oscillators. In particular, recent experiments revealed the existence of complex spatiotemporal dynamics for systems consisting of coupled micelles (V < 10(-21) L) or droplets (V ≈ [10(-8)-10(-11)] L) in which the pBZ reaction takes place. These results have been mostly understood in terms of reaction-diffusion models. However, in view of the small size of the droplets and micelles, large fluctuations of concentrations are to be expected...
August 15, 2017: Physical Chemistry Chemical Physics: PCCP
Akira Kusaba, Guanchen Li, Michael R von Spakovsky, Yoshihiro Kangawa, Koichi Kakimoto
Clearly understanding elementary growth processes that depend on surface reconstruction is essential to controlling vapor-phase epitaxy more precisely. In this study, ammonia chemical adsorption on GaN(0001) reconstructed surfaces under metalorganic vapor phase epitaxy (MOVPE) conditions (3Ga-H and Nad-H + Ga-H on a 2 × 2 unit cell) is investigated using steepest-entropy-ascent quantum thermodynamics (SEAQT). SEAQT is a thermodynamic-ensemble based, first-principles framework that can predict the behavior of non-equilibrium processes, even those far from equilibrium where the state evolution is a combination of reversible and irreversible dynamics...
August 15, 2017: Materials
David Coles, Lucas C Flatten, Thomas Sydney, Emily Hounslow, Semion K Saikin, Alán Aspuru-Guzik, Vlatko Vedral, Joseph Kuo-Hsiang Tang, Robert A Taylor, Jason M Smith, David G Lidzey
Photosynthetic organisms rely on a series of self-assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna-Matthews-Olson complex to the reaction center...
August 15, 2017: Small
Adil Majeed Rather, Sulendar Mahato, Kousik Maji, Neeha Gogoi, Uttam Manna
Controlled and sustained release of drug-like small molecules in an aqueous medium still remains a challenging problem due to rapid infiltration of liquid water in most reported drug release systems. However, internal-superhydrophobicity with an antifouling property extending beyond the surface of a material recently has been recognized as a potential avenue for sustained and extended release of drug-like small molecules. Sluggish removal of metastable trapped air in a superhyrophobic material provides a basis to achieve extended release of encapsulated small molecules...
August 15, 2017: Nanoscale
Jing Zhang, Yang Li, Ruoyu Xu, Yiyun Chen
The alkoxyl radical is an essential and prevalent reactive intermediate for chemical and biological studies. Here we report the first donor-acceptor complex-enabled alkoxyl radical generation under metal-free reaction conditions induced by visible light. Hantzsch ester forms the key donor-acceptor complex with N-alkoxyl derivatives, which is elucidated by a series of spectrometry and mechanistic experiments. Selective C(sp3)-C(sp3) bond cleavage and allylation/alkenylation is demonstrated for the first time using this photocatalyst-free approach with linear primary, secondary, and tertiary alkoxyl radicals...
August 15, 2017: Angewandte Chemie
Linda Ahammer, Sarina Grutsch, Michael Wallner, Fatima Ferreira, Martin Tollinger
In Northern America and Europe a great number of people are suffering from birch pollen allergy and pollen related food allergies. The trigger for these immunological reactions is the 17.5 kDa major birch pollen allergen Bet v 1, which belongs to the family of PR-10 (pathogenesis-related) proteins. In nature, Bet v 1 occurs as a mixture of various isoforms that possess different immunological properties despite their high sequence identities. Bet v 1.0102 (Bet v 1d), which is investigated here, is a hypoallergenic isoform of Bet v 1 and a potential candidate for allergen-specific immunotherapy...
August 14, 2017: Biomolecular NMR Assignments
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