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https://www.readbyqxmd.com/read/28724108/yellow-perch-perca-flavescens-mercury-unaffected-by-wildland-fires-in-northern-minnesota
#1
Charlotte E Riggs, Randall K Kolka, Edward A Nater, Emma L Witt, Trent R Wickman, Laurel G Woodruff, Jason T Butcher
Wildland fire can alter mercury (Hg) cycling on land and in adjacent aquatic environments. In addition to enhancing local atmospheric Hg redeposition, fire can influence terrestrial movement of Hg and other elements into lakes via runoff from burned upland soil. However, the impact of fire on water quality and the accumulation of Hg in fish remain equivocal. We investigated the effects of fire-specifically, a low-severity prescribed fire and moderate-severity wildfire-on young-of-the-year yellow perch () and lake chemistry in a small remote watershed in the Boundary Waters Canoe Area Wilderness in northeastern Minnesota...
May 2017: Journal of Environmental Quality
https://www.readbyqxmd.com/read/28723063/using-cooperatively-folded-peptides-to-measure-interaction-energies-and-conformational-propensities
#2
Maziar S Ardejani, Evan T Powers, Jeffery W Kelly
The rates and equilibria of the folding of biopolymers are determined by the conformational preferences of the subunits that make up the sequence of the biopolymer and by the interactions that are formed in the folded state in aqueous solution. Because of the centrality of these processes to life, quantifying conformational propensities and interaction strengths is vitally important to understanding biology. In this Account, we describe our use of peptide model systems that fold cooperatively yet are small enough to be chemically synthesized to measure such quantities...
July 19, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28722399/bias-free-chemically-diverse-test-sets-from-machine-learning
#3
Ellen Swann, Michael Fernandez, Michelle L Coote, Amanda S Barnard
Current benchmarking methods in quantum chemistry rely on databases that are built using a chemist's intuition. It is not fully understood how diverse or representative these databases truly are. Multivariate statistical techniques like archetypal analysis and K-means clustering have previously been used to summarise large sets of nanoparticles however molecules are more diverse and not as easily characterised by descriptors. In this work we compare three sets of descriptors based on the one-, two- and three-dimensional structure of a molecule...
July 19, 2017: ACS Combinatorial Science
https://www.readbyqxmd.com/read/28722305/dynamic-covalent-chemistry-of-aldehyde-enamines-bi-iii-and-sc-iii-catalysis-of-amine-enamine-exchange
#4
Yang Zhang, Sheng Xie, Mingdi Yan, Olof Ramström
The dynamic exchange of enamines from secondary amines and enolizable aldehydes has been demonstrated in organic solvents. The enamine exchange with amines was efficiently catalyzed by Bi(OTf)3 and Sc(OTf)3 (2 mol%) and the equilibria (60 mM) could be attained within hours at room temperature. The formed dynamic covalent systems displayed high stabilities in basic environment with < 2% by-product formation within one week after complete equilibration. This study expands the scope of dynamic C-N bonds from imine chemistry to enamines, enabling further dynamic methodologies in exploration of this important class of structures in systems chemistry...
July 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28722282/metal-free-nitrile-diboration-through-activation-by-an-electron-rich-diborane
#5
Markus Frick, Elisabeth Kaifer, Hans-Jörg Himmel
Diboration of unsaturated organic compounds is an extremely useful reaction in synthetic chemistry. Herein we report the first diboration of a nitrile by an electron-rich diborane, mediated by an electrophilic borane. The reaction is metal-free, and all reagents are readily available.
July 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28719022/engineering-the-surface-of-smart-nanocarriers-using-a-ph-thermal-gsh-responsive-polymer-zipper-for-precise-tumor-targeting-therapy-in-vivo
#6
Penghui Zhang, Yan Wang, Jing Lian, Qi Shen, Chen Wang, Bohan Ma, Yuchao Zhang, Tingting Xu, Jianxin Li, Yongping Shao, Feng Xu, Jun-Jie Zhu
Nanocarrier surface chemistry plays a vital role in mediating cell internalization and enhancing delivery efficiency during in vivo chemotherapy. Inspired by the ability of proteins to alter their conformation to mediate functions, a pH-/thermal-/glutathione-responsive polymer zipper consisting of cell-penetrating poly(disulfide)s and thermosensitive polymers bearing guanidinium/phosphate (Gu(+) /pY(-) ) motifs to spatiotemporally tune the surface composition of nanocarriers for precise tumor targeting and efficient drug delivery is developed...
July 18, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28719021/high-temperature-ionic-epitaxy-of-halide-perovskite-thin-film-and-the-hidden-carrier-dynamics
#7
Yiping Wang, Xin Sun, Zhizhong Chen, Yi-Yang Sun, Shengbai Zhang, Toh-Ming Lu, Esther Wertz, Jian Shi
High-temperature vapor phase epitaxy (VPE) has been proved ubiquitously powerful in enabling high-performance electro-optic devices in III-V semiconductor field. A typical example is the successful growth of p-type GaN by VPE for blue light-emitting diodes. VPE excels as it controls film defects such as point/interface defects and grain boundary, thanks to its high-temperature processing condition and controllable deposition rate. For the first time, single-crystalline high-temperature VPE halide perovskite thin film has been demonstrated-a unique platform on unveiling previously uncovered carrier dynamics in inorganic halide perovskites...
July 18, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28718919/putting-rings-around-carbon-nanotubes
#8
Emilio M Pérez
In the last five years, we have developed synthetic methods towards encapsulation of single walled carbon nanotubes (SWNTs) into organic macrocycles, to form rotaxane-type molecules. These are the first examples of mechanically interlocked SWNTs derivatives (MINTs). In this article, I discuss our motivation to continue developing chemistry of SWNTs at a time well past their hype. We explain our synthetic strategy and characterization methodology in detail, stressing the general aspects. In particular, we emphasize the importance of adequate control experiments and bulk spectroscopic and analytical data to determine the structure of SWNT derivatives, as opposed to relying only (or mostly) on microscopy...
July 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28718644/general-and-direct-method-for-preparing-oligonucleotide-functionalized-metal-organic-framework-nanoparticles
#9
Shunzhi Wang, C Michael McGuirk, Michael B Ross, Shuya Wang, Pengcheng Chen, Hang Xing, Yuan Liu, Chad A Mirkin
Metal-organic frameworks (MOFs) are a class of modular, crystalline, and porous materials that hold promise for storage and transport of chemical cargoes. Though MOFs have been studied in bulk forms, ways of deliberately manipulating the external surface functionality of MOF nanoparticles are less developed. A generalizable approach to modify their surfaces would allow one to impart chemical functionality onto the particle surface that is independent of the bulk MOF structure. Moreover, the use of a chemically programmable ligand, such as DNA, would allow for the manipulation of interparticle interactions...
July 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28718642/predictive-model-for-site-selective-aryl-and-heteroaryl-c-h-functionalization-via-organic-photoredox-catalysis
#10
Kaila A Margrey, Joshua B McManus, Simone Bonazzi, Frederic Zecri, David A Nicewicz
Direct C-H functionalization of aromatic compounds is a useful synthetic strategy that has garnered much attention due to its application to pharmaceuticals, agrochemicals, and late stage functionalization reactions on complex molecules. Based on previous methods disclosed by our lab, we sought to develop a predictive model for site selectivity and extend this aryl functionalization chemistry to a selected set of heteroaromatic systems commonly used in the pharmaceutical industry. Using electron density calculations, we were able to predict site selectivity of direct C-H functionalization in a number of heterocycles and identify general trends observed across heterocycle classes...
July 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28717021/genetic-and-metabolic-engineering-in-diatoms
#11
REVIEW
Weichao Huang, Fayza Daboussi
Diatoms have attracted considerable attention due to their success in diverse environmental conditions, which probably is a consequence of their complex origins. Studies of their metabolism will provide insight into their adaptation capacity and are a prerequisite for metabolic engineering. Several years of investigation have led to the development of the genome engineering tools required for such studies, and a profusion of appropriate tools is now available for exploring and exploiting the metabolism of these organisms...
September 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28715772/stability-of-single-dispersed-silver-nanoparticles-in-natural-and-synthetic-freshwaters-effects-of-dissolved-oxygen
#12
Xiaoyan Zou, Penghui Li, Jie Lou, Xiaoyan Fu, Hongwu Zhang
Silver nanoparticles (AgNPs) are increasingly used in various commercial products. This increased use raises ecological concerns because of the large release of AgNPs into the environment. Once released, the local water chemistry has the potential to influence the environmental fates and behaviors of AgNPs. The impacts of dissolved oxygen and natural organic matter (NOM) on the dissolution and stability of AgNPs were investigated in synthetic and natural freshwaters for 7 days. In synthetic freshwater, the aggregation of AgNPs occurred due to the compression of the electric double layer, accompanied by the dissolution of AgNPs...
July 14, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28715190/chemical-topic-modeling-exploring-molecular-datasets-using-a-common-text-mining-approach
#13
Nadine Schneider, Nikolas Fechner, Gregory A Landrum, Nikolaus Stiefl
Big data is one of the key transformative factors which are increasingly influencing all aspects of modern life. Although this transformation brings vast opportunities it also generates novel challenges, not the least of which is organizing and searching this data deluge. The field of medicinal chemistry is not different: more and more data are being generated, for instance by technologies such as DNA encoded libraries, peptide libraries, text mining of large literature corpora, and new in silico enumeration methods...
July 17, 2017: Journal of Chemical Information and Modeling
https://www.readbyqxmd.com/read/28714671/a-facile-method-for-the-preparation-of-covalent-triazine-framework-coated-monoliths-as-catalyst-support-applications-in-c1-catalysis
#14
Anastasiya V Bavykina, Alma Itzel Olivos Suarez, Dmitrii Osadchii, Rahul Valecha, Robert Franz, Michiel Makkee, Freek Kapteijn, Jorge Gascon
A quasi Chemical Vapour Deposition method for the manufacturing of well-defined Covalent Triazine Framework (CTF) coatings on cordierite monoliths is reported. The resulting supported porous organic polymer is an excellent support for the immobilisation of two different homogeneous catalysts: 1) an IrIIICp*-based catalyst for the hydrogen production from formic acid, and 2) a PtII-based for the direct activation of methane via Periana chemistry. The immobilised catalysts display a much higher activity in comparison with the unsupported CTF operated in slurry because of improved mass transport...
July 17, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28713354/microbial-populations-of-stony-meteorites-substrate-controls-on-first-colonizers
#15
Alastair W Tait, Emma J Gagen, Siobhan A Wilson, Andrew G Tomkins, Gordon Southam
Finding fresh, sterilized rocks provides ecologists with a clean slate to test ideas about first colonization and the evolution of soils de novo. Lava has been used previously in first colonizer studies due to the sterilizing heat required for its formation. However, fresh lava typically falls upon older volcanic successions of similar chemistry and modal mineral abundance. Given enough time, this results in the development of similar microbial communities in the newly erupted lava due to a lack of contrast between the new and old substrates...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28709053/transport-and-retention-of-biochar-nanoparticles-in-a-paddy-soil-under-environmentally-relevant-solution-chemistry-conditions
#16
Ming Chen, Dengjun Wang, Fan Yang, Xiaoyun Xu, Nan Xu, Xinde Cao
Land application of biochar has been increasingly recommended as a powerful strategy for carbon sequestration and soil remediation. However, the biochar particles, especially those in the nanoscale range, may migrate or carry the inherent contaminants along the soil profile, posing a potential risk to the groundwater. This study investigated the transport and retention of wood chip-derived biochar nanoparticles (NPs) in water-saturated columns packed with a paddy soil. The environmentally-relevant soil solution chemistry including ionic strength (0...
July 11, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28708381/microfabrication-of-monolithic-microfluidic-platforms-using-low-temperature-co-fired-ceramics-suitable-for-fluorescence-imaging
#17
Pedro Couceiro, Julián Alonso-Chamarro
In this work, the influence of laser ablation and lamination parameters in the fabrication of embedded microstructures using Low Temperature Co-Fired Ceramics, have been studied. First, the influence of laser ablation parameters in the dimensions of fabricated microchannels in Low Temperature Co-Fired Ceramics substrates was characterized and strategies for tailoring the microchannels aspect ratios are described. The influence of lamination conditions on the fabrication of monolithically embedded microstructures is presented...
July 14, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28707900/aerosol-fragmentation-driven-by-coupling-of-acid-base-and-free-radical-chemistry-in-the-heterogeneous-oxidation-of-aqueous-citric-acid-by-oh-radicals
#18
Matthew J Liu, Aaron A Wiegel, Kevin R Wilson, Frances A Houle
A key uncertainty in the heterogeneous oxidation of carboxylic acids by hydroxyl radicals (OH) in aqueous phase aerosol is how the free radical reaction pathways might be altered by acid-base chemistry. In particular, if acid-base reactions occur concurrently with acyloxy radical formation and unimolecular decomposition of alkoxy radicals, there is a possibility that differences in reaction pathways impact the partitioning of organic carbon between the gas and aqueous phases. To examine these questions, a kinetic model is developed for the OH initiated oxidation of citric acid aerosol at high relative humidity...
July 14, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28707618/how-high-pressure-unifies-solvation-processes-in-liquid-chromatography
#19
Szymon Bocian, Tea Škrinjar, Tomislav Bolanca, Bogusław Buszewski
A series of core–shell-based stationary phases of varying surface chemistry were subjected to solvent adsorption investigation under ultra-HPLC conditions. Acetonitrile and water excess isotherms were measured using a minor disturbance method. It was observed that adsorption of organic solvent is unified under high pressure. Preferential solvation due to specific interactions between the stationary phases and solvent molecules was limited. The obtained results showed that the solvation process is almost independent of surface chemistry, in contrast to HPLC conditions in which specific interactions differentiate solvation processes...
July 13, 2017: Journal of AOAC International
https://www.readbyqxmd.com/read/28704030/chemistry-is-dead-long-live-chemistry
#20
Luke D Lavis
Chemistry, once king of fluorescence microscopy, was usurped by the field of fluorescent proteins. The increased demands of modern microscopy techniques on the "photon budget" requires better and brighter fluorophores. Here, we review the recent advances in biochemistry, protein engineering, and organic synthesis that have allowed a triumphant return of chemical dyes to modern biological imaging.
July 13, 2017: Biochemistry
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