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https://www.readbyqxmd.com/read/29045933/chemical-transformation-of-silver-nanoparticles-in-aquatic-environments-mechanism-morphology-and-toxicity
#1
REVIEW
Weicheng Zhang, Bangding Xiao, Tao Fang
Silver nanoparticles (Ag NPs) have been inevitably introduced into ecological environment during their extensive applications in daily human life. Thermodynamically, Ag NPs are unstable and transform into other species under various aqueous conditions. Ag NPs and their transformation products pose potential threats to environment and humans. However, the complex environmental conditions and transformations of Ag NPs complicate their human health and environmental risk assessment. To bridge the knowledge gap, four essential environmental transformations, oxidative dissolution, sulfidation, chlorination and photoreduction, of Ag NPs are reviewed herein...
October 3, 2017: Chemosphere
https://www.readbyqxmd.com/read/29045929/deciphering-the-complexation-process-of-a-fluoroquinolone-antibiotic-levofloxacin-with-bovine-serum-albumin-in-the-presence-of-additives
#2
Amandeep Kaur, Imran Ahmd Khan, Parampaul Kaur Banipal, Tarlok Singh Banipal
The current work aims to explore the thermodynamic and conformational aspects for the binding of fluoroquinolone antibacterial drug, levofloxacin (LFC), with bovine serum albumin (BSA) using calorimetric, spectroscopic (UV-visible, fluorescence, circular dichroism, and (1)H NMR), dynamic light scattering (DLS) and computational methods (molecular docking). The binding of LFC with BSA at two sequential sites with higher affinity (~10(3)M(-1)) at the first site has been explored by calorimetry whereas the binding at a single site with affinity of the order of ~10(4)M(-1) has been observed from fluorescence spectroscopy...
October 9, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/29045869/metastability-gap-in-the-phase-diagram-of-monoclonal-igg-antibody
#3
Jacob B Rowe, Rachel A Cancel, Tyler D Evangelous, Rhiannon P Flynn, Sergei Pechenov, J Anand Subramony, Jifeng Zhang, Ying Wang
Crystallization of IgG antibodies has important applications in the fields of structural biology, biotechnology, and biopharmaceutics. However, a rational approach to crystallize antibodies is still lacking. In this work, we report a method to estimate the solubility of antibodies at various temperatures. We experimentally determined the full phase diagram of an IgG antibody. Using the full diagram, we examined the metastability gaps, i.e., the distance between the crystal solubility line and the liquid-liquid coexistence curve, of IgG antibodies...
October 17, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/29045793/adsorption-removal-of-glycidyl-esters-from-palm-oil-and-oil-model-solution-by-using-acid-washed-oil-palm-wood-based-activated-carbon-kinetic-and-mechanism-study
#4
Weiwei Cheng, Guoqin Liu, Xuede Wang, Lipeng Han
Acid-washed oil palm wood-based activated carbon (OPAC) has been investigated for its potential application as a promising adsorbent in the removal of glycidyl esters (GEs) from both palm oil and oil model (hexadecane) solution. It was observed that the removal rate of GEs in palm oil was up to >95%, which was significantly higher than other adsorbents used in this study. In batch adsorption system, the adsorption efficiency and performance of acid-washed OPAC were evaluated as a function of several experimental parameters such as contact time, initial glycidyl palmitate (PGE) concentration, adsorbent dose, and temperature...
October 18, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/29045134/effects-of-the-ph-on-the-formation-and-doping-mechanisms-of-zno-nanowires-using-aluminum-nitrate-and-ammonia
#5
Claire Verrier, Estelle Appert, Odette Chaix-Pluchery, Laetitia Rapenne, Quentin Rafhay, Anne Kaminski-Cachopo, Vincent Consonni
The elucidation of the fundamental processes in aqueous solution during the chemical bath deposition of ZnO nanowires (NWs) using zinc nitrate and hexamethylenetetramine is of great significance: however, their extrinsic doping by foreign elements for monitoring their optical and electrical properties is still challenging. By combining thermodynamic simulations yielding theoretical solubility plots and speciation diagrams with in situ pH measurements and structural, chemical, and optical analyses, we report an in-depth understanding of the pH effects on the formation and aluminum doping mechanisms of ZnO NWs...
October 18, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/29044986/spectroscopic-investigation-of-the-anticancer-alkaloid-piperlongumine-binding-to-human-serum-albumin-from-the-viewpoint-of-drug-delivery
#6
Yu Liu, Qian-Yu Li, Yu-Ping Wang, Yi-Ming Liu, Bin Liu, Mei-Mei Liu, Bing-Mi Liu
Piperlongumine (PL) is a very promising natural agent with a high potential for cancer treatment. To overcome the poor water solubility of PL, there is a need to develop a novel water-soluble formulation in which PL is non-covalently bound to human serum albumin (HSA). PL binding to HSA was studied by various spectroscopic techniques under simulated physiological conditions. Spectroscopic evidence showed that the interaction of PL with HSA could form a PL-HSA complex. The binding constant (Ka ) values increased with increasing temperature, and a similar dependence was observed for the number of binding sites (n) values...
October 18, 2017: Luminescence: the Journal of Biological and Chemical Luminescence
https://www.readbyqxmd.com/read/29044500/water-and-salt-migration-with-phase-change-in-saline-soil-during-freezing-and-thawing-processes
#7
Daoyong Wu, Xiangyang Zhou, Xingyuan Jiang
Water and salt transfer coupled with phase change may cause serious damage to engineering structures in saline soil regions. In this study, the migration of water and salt in silty clay collected from the Qinghai-Tibet Plateau is explored experimentally and numerically during freezing and thawing processes. The results revealed that there are significant differences in the variations of liquid water content and solution concentration for different initial salt contents, due to salt crystallization and dissolution...
October 17, 2017: Ground Water
https://www.readbyqxmd.com/read/29044258/the-reaction-of-c5n-with-acetylene-as-a-possible-intermediate-step-to-produce-large-anions-in-titan-s-ionosphere
#8
Carl Fredrik Lindén, Ján Žabka, Miroslav Polášek, Illia Zymak, Wolf D Geppert
A theoretical and experimental investigation of the reaction C5N(-) + C2H2 has been carried out. This reaction is of astrophysical interest since the growth mechanism of large anions that have been detected in Titan's upper atmosphere by the Cassini plasma spectrometer are still largely unknown. The experimental studies have been performed using a tandem quadrupole mass spectrometer which allows identification of the different reaction channels and assessment of their reaction thresholds. Results of these investigations were compared with the predictions of ab initio calculations, which identified possible pathways leading to the observed products and their thermodynamical properties...
October 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29044121/robust-bain-distortion-in-the-premartensite-phase-of-a-platinum-substituted-ni2mnga-magnetic-shape-memory-alloy
#9
Sanjay Singh, B Dutta, S W D'Souza, M G Zavareh, P Devi, A S Gibbs, T Hickel, S Chadov, C Felser, D Pandey
The premartensite phase of shape memory and magnetic shape memory alloys (MSMAs) is believed to be a precursor state of the martensite phase with preserved austenite phase symmetry. The thermodynamic stability of the premartensite phase and its relation to the martensitic phase is still an unresolved issue, even though it is critical to the understanding of the functional properties of MSMAs. We present here unambiguous evidence for macroscopic symmetry breaking leading to robust Bain distortion in the premartensite phase of 10% Pt-substituted Ni2MnGa...
October 18, 2017: Nature Communications
https://www.readbyqxmd.com/read/29044050/on-atomic-mechanisms-governing-the-oxidation-of-bi-sub-2-sub-te-sub-3-sub
#10
Denis Music, Keke Chang, Paul Schmidt, Felix N Braun, Martin Heller, Steffen Hermsen, Peter J Pöllmann, Till Schulzendorff, Cedric Wagner
Oxidation of Bi2Te3 (space group R-3m) has been investigated using experimental and theoretical means. Based on calorimetry, x-ray photoelectron spectroscopy and thermodynamic modelling, Bi2Te3 is at equilibrium with Bi2O3 and TeO2, whereby the most stable compound is Bi2Te3, followed by Bi2O3. Hence, the reactivity of Bi towards oxygen is expected to be higher than that of Te. This notion is supported by density functional theory. The strongest bond is formed between Bi and Te, followed by Bi - O. This gives rise to unanticipated atomic processes...
October 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/29043810/structure-and-thermodynamics-of-metal-clusters-on-atomically-smooth-substrates
#11
Marco Eckhoff, Dmitri Schebarchov, David J Wales
We analyse the structure of model Ni$_{N}$ and Cu$_{N}$ clusters ($N=55$, $147$) supported on a variety of atomically smooth van der Waals surfaces. The global minima are mapped in the space of two parameters: (i) the laterally averaged surface stickiness, $\gamma$, which controls the macroscopic wetting angle; and (ii) the surface microstructure, which produces more subtle but important templating via epitaxial stresses. We find that adjusting the substrate lattice (even at constant $gamma$) can favour different crystal plane orientations in the cluster, stabilise hexagonal close-packed order, or induce various defects, such as stacking faults, twin boundaries, and fivefold disclinations...
October 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29043801/compressibility-anomalies-in-stretched-water-and-their-interplay-with-density-anomalies
#12
Vincent Holten, Chen Qiu, Emmanuel Guillerm, Max Wilke, Jaroslav Ricka, Martin Frenz, Frédéric Caupin
Water keeps puzzling scientists because of its numerous properties which behave oppositely to usual liquids: for instance, water expands upon cooling, and liquid water is denser than ice. To explain this anomalous behaviour, several theories have been proposed, with different predictions for the properties of supercooled water (liquid at conditions where ice is stable). However, discriminating between those theories with experiments has remained elusive because of spontaneous ice nucleation. Here we measure the sound velocity in liquid water stretched to negative pressure, and derive an experimental equation of state, which reveals compressibility anomalies...
October 18, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29043359/selective-recognition-of-quaternary-ammonium-ions-and-zwitterions-by-using-a-biomimetic-bis-calix-6-arene-based-receptor
#13
Steven Moerkerke, Volodymyr Malytskyi, Lionel Marcélis, Johan Wouters, Ivan Jabin
Artificial receptors able to recognize efficiently chemical species bearing a quaternary ammonium group have potential applications in the fields of biological and environmental analyses. A possible biomimetic strategy for the elaboration of such receptors consists of associating in close proximity a polyaromatic cavity with a polar binding site. Herein, we show that bis-calix[6]arene 1 behaves as a heteroditopic receptor that can bind biologically relevant quaternary ammonium ions and zwitterions. This host can selectively extract carbamylcholine G3 from water, opening the way for the sensing of this acetylcholine agonist...
October 18, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29043353/machine-learnt-bond-order-potential-to-model-metal-organic-co-c-heterostructures
#14
Badri Narayanan, Henry Chan, Alper Kinaci, Fatih G Sen, Stephen K Gray, Maria K Y Chan, Subramanian K R S Sankaranarayanan
A fundamental understanding of the inter-relationships between structure, morphology, atomic scale dynamics, chemistry, and physical properties of mixed metallic-covalent systems is essential to design novel functional materials for applications in flexible nano-electronics, energy storage and catalysis. To achieve such knowledge, it is imperative to develop robust and computationally efficient atomistic models that describe atomic interactions accurately within a single framework. Here, we present a unified Tersoff-Brenner type bond order potential (BOP) for a Co-C system, trained against lattice parameters, cohesive energies, equation of state, and elastic constants of different crystalline phases of cobalt as well as orthorhombic Co2C derived from density functional theory (DFT) calculations...
October 18, 2017: Nanoscale
https://www.readbyqxmd.com/read/29043323/concomitant-polymorphism-and-the-martensitic-like-transformation-of-an-organic-crystal
#15
Michael T Ruggiero, J Axel Zeitler, Timothy M Korter
Crystalline polymorphism is a phenomenon that occurs in many molecular solids, resulting in a diverse range of possible bulk structures. Temperature and pressure can often be used to thermodynamically control which crystal form is preferred, and the associated transitions between polymorphic phases are often discontinuous and complete. N-Methyl-4-carboxypyridinium chloride is a solid that undergoes an apparent continuous temperature-dependent phase transition from an orthorhombic to a monoclinic polymorph. However, a hybrid characterization approach using single-crystal X-ray diffraction, terahertz time-domain spectroscopy, and solid-state density functional theory reveals the transformation to be actually a slowly changing ratio of the two discrete polymorphic forms...
October 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29043322/chirality-in-adsorption-on-solid-surfaces
#16
REVIEW
Francisco Zaera
In the present review we survey the main advances made in recent years on the understanding of chemical chirality at solid surfaces. Chirality is an important topic, made particularly relevant by the homochiral nature of the biochemistry of life on Earth, and many chiral chemical reactions involve solid surfaces. Here we start our discussion with a description of surface chirality and of the different ways that chirality can be bestowed on solid surfaces. We then expand on the studies carried out to date to understand the adsorption of chiral compounds at a molecular level...
October 18, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/29042617/expression-and-function-of-abcg4-in-the-mouse-blood-brain-barrier-role-in-restricting-the-brain-entry-of-amyloid-%C3%AE-peptide
#17
Agnès Dodacki, Matthew Wortman, Bruno Saubaméa, Stéphanie Chasseigneaux, Sophie Nicolic, Nathalie Prince, Murielle Lochus, Anne-Laure Raveu, Xavier Declèves, Jean-Michel Scherrmann, Shailendra B Patel, Fanchon Bourasset
ABCG4 is an ATP-binding cassette transmembrane protein which has been shown, in vitro, to participate in the cellular efflux of desmosterol and amyloid-β peptide (Aβ). ABCG4 is highly expressed in the brain, but its localization and function at the blood-brain barrier (BBB) level remain unknown. We demonstrate by qRT-PCR and confocal imaging that mouse Abcg4 is expressed in the brain capillary endothelial cells. Modelling studies of the Abcg4 dimer suggested that desmosterol showed thermodynamically favorable binding at the putative sterol-binding site, and this was greater than for cholesterol...
October 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/29042336/physicochemical-properties-of-inclusion-complexes-of-highly-soluble-%C3%AE-cyclodextrins-with-highly-hydrophobic-testosterone-propionate
#18
Christian Celia, Angela Scala, Rosanna Stancanelli, Emanuela Surdo, Donatella Paolino, Alessandro Grattoni, Nicola Micale, Vincenza Crupi, Domenico Majolino, Massimo Fresta, Silvana Tommasini, Valentina Venuti, Cinzia Anna Ventura
Hydroxypropyl-β-cyclodextrin (HP-β-CyD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CyD) were used to generate hydrophilic complexes of the poorly water-soluble drug testosterone propionate (TP). The inclusion complexes were obtained by freeze-drying, and then analyzed at both liquid and solid states. Phase solubility studies, performed according to the type-AL solubility diagrams of TP in presence of both CyDs, suggested the formation of water-soluble complexes at 1:1 molar ratio. These results were confirmed by continuous variation method (Job's plot)...
October 14, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/29042237/ligand-partitioning-into-lipid-bilayer-membranes-under-high-pressure-implication-of-variation-in-phase-transition-temperatures
#19
Hitoshi Matsuki, Kentaro Kato, Hirotsugu Okamoto, Shuntaro Yoshida, Masaki Goto, Nobutake Tamai, Shoji Kaneshina
The variation in phase-transition temperatures of dipalmitoylphosphatidylcholine (DPPC) bilayer membrane by adding two membrane-active ligands, a long-chain fatty acid (palmitic acid (PA)) and an inhalation anesthetic (halothane (HAL)), was investigated by light-transmittance measurements and fluorometry. By assuming the thermodynamic colligative property for the bilayer membrane at low ligand concentrations, the partitioning behavior of these ligands into the DPPC bilayer membrane was considered. It was proved from the differential partition coefficients between two phases that PA has strong affinity with the gel (lamellar gel) phase in a micro-molal concentration range and makes the bilayer membrane more ordered while HAL has strong affinity with the liquid crystalline phase in a milli-molal concentration range and does the bilayer membrane more disordered...
October 14, 2017: Chemistry and Physics of Lipids
https://www.readbyqxmd.com/read/29041619/near-field-thermal-upconversion-and-energy-transfer-through-a-kerr-medium
#20
Chinmay Khandekar, Alejandro W Rodriguez
We present an approach for achieving large Kerr χ((3))-mediated thermal energy transfer at the nanoscale that exploits a general coupled-mode description of triply resonant, four-wave mixing processes. We analyze the efficiency of thermal upconversion and energy transfer from mid- to near-infrared wavelengths in planar geometries involving two slabs supporting far-apart surface plasmon polaritons and separated by a nonlinear χ((3)) medium that is irradiated by externally incident light. We study multiple geometric and material configurations and different classes of intervening mediums-either bulk or nanostructured lattices of nanoparticles embedded in nonlinear materials-designed to resonantly enhance the interaction of the incident light with thermal slab resonances...
September 18, 2017: Optics Express
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