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https://www.readbyqxmd.com/read/28651318/fate-of-polycyclic-aromatic-hydrocarbons-from-the-north-pacific-to-the-arctic-field-measurements-and-fugacity-model-simulation
#1
Hongwei Ke, Mian Chen, Mengyang Liu, Meng Chen, Mengshan Duan, Peng Huang, Jiajun Hong, Yan Lin, Shayen Cheng, Xuran Wang, Mengxue Huang, Minggang Cai
Polycyclic aromatic hydrocarbons (PAHs) have accumulated ubiquitously inArctic environments, where re-volatilization of certain organic pollutants as a result of climate change has been observed. To investigate the fate of semivolatile organic compounds in the Arctic, dissolved PAHs in the surface seawaters from the temperate Pacific Ocean to the Arctic Ocean, as well as a water column in the Arctic Ocean, were collected during the 4th Chinese National Arctic Research Expedition in summer 2010. The total concentrations of seven dissolved PAHs in surface water ranged from 1...
June 16, 2017: Chemosphere
https://www.readbyqxmd.com/read/28651056/significantly-improved-protein-folding-thermodynamics-using-a-dispersion-corrected-water-model-and-a-new-residue-specific-force-field
#2
Hao-Nan Wu, Fan Jiang, Yun-Dong Wu
An accurate potential energy model is crucial for biomolecular simulations. Despite many recent improvements of classical protein force fields, there are remaining key issues: much weaker temperature-dependence of folding/unfolding equilibrium, and overly collapsed unfolded or disordered states. For the later problem, a new water model (TIP4P-D) has been proposed to correct the significantly underestimated water dispersion interactions. Here, using TIP4P-D, we reveal problems in current force fields through failures in folding model systems (a polyalanine peptide, Trp-cage and the GB1 hairpin)...
June 26, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28651021/natural-immune-response-to-plasmodium-vivax-alpha-helical-coiled-coil-protein-motifs-and-its-association-with-the-risk-of-p-vivax-malaria
#3
Nora Céspedes, Connie S N Li Wai Suen, Cristian Koepfli, Camila T França, Ingrid Felger, Issa Nebie, Myriam Arévalo-Herrera, Ivo Mueller, Giampietro Corradin, Sócrates Herrera
Protein α-helical coiled coil structures are known to induce antibodies able to block critical functions in different pathogens. In a previous study, a total of 50 proteins of Plasmodium vivax erythrocytic asexual stages containing α-helical coiled coil structural motifs were identified in silico, and the corresponding peptides were chemically synthesized. A total of 43 peptides were recognized by naturally acquired antibodies in plasma samples from both Papua New Guinea (PNG) and Colombian adult donors. In this study, the association between IgG antibodies to these peptides and clinical immunity was further explored by measuring total IgG antibody levels to 24 peptides in baseline samples from a longitudinal study of children aged 1-3 years (n = 164) followed for 16 months...
2017: PloS One
https://www.readbyqxmd.com/read/28650617/kinetics-and-mechanism-of-the-autocatalytic-oxidation-of-bis-terpyridine-iron-ii-by-peroxomonosulfate-ion-oxone-in-acidic-medium
#4
Gábor Bellér, Gábor Lente, István Fábián
The autocatalytic oxidation of the bis(terpyridine)iron(II) complex, Fe(tpy)2(2+) by peroxomonosulfate ion (PMS) proceeds via the formation of the corresponding iron(III) complex (Fe(tpy)2(3+)) as the primary oxidation product. The proton-assisted dissociation of Fe(tpy)2(2+) and subsequent oxidation of Fe(2+) are side reactions in this system. In the initial stage of the reaction, a 1:1 adduct is formed between PMS and bis(terpyridine)iron(II), which decomposes in an intramolecular electron transfer reaction step...
June 26, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28650586/a-complete-thermodynamic-analysis-of-enzyme-turnover-links-the-free-energy-landscape-to-enzyme-catalysis
#5
Hannah Bl Jones, Stephen A Wells, Erica J Prentice, Anthony Kwok, Liyin L Liang, Vickery L Arcus, Christopher R Pudney
Our understanding of how enzymes work is colored by static structure depictions where the enzyme scaffold is presented as either immobile, or in equilibrium between well-defined static conformations. Proteins however exhibit a large degree of motion over a broad range of timescales and magnitudes and this is defined thermodynamically by the enzyme free energy landscape (FEL). The role and importance of enzyme motion is extremely contentious. Much of the challenge is in the experimental detection of so called 'conformational sampling' involved in enzyme turnover...
June 26, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28650088/two-structurally-characterized-conformational-isomers-with-different-c-p-bonds
#6
Herbert W Roesky, Sudipta Roy, Kartik Chandra Mondal, Bin Li, Subrata Kundu, Christian J Schürmann, Sayan Dutta, Debasis Koley, Dietmar Stalke, Regine Herbst-Irmer
The cyclic alkyl(amino) carbene (cAAC) bonded chlorophosphinidene (cAAC)P-Cl (2/2´) was isolated from the direct reaction between cAAC and phosphorus trichloride (PCl3). Compound 2/2´ has been characterized by NMR and mass spectrometry. 31P NMR investigations [~160 ppm (major) and ~130 ppm (minor)] structural determination reveal that there are two different P environments of P-Cl unit. X-ray single crystal determination suggests a co-crystallization of two conformational isomers of (cAAC)P-Cl (2/2´); the major compound possessing a cAAC-PCl unit with CcAAC-P 1...
June 26, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28650034/the-sandpile-revisited-computer-assisted-determination-of-constitutive-relations-and-the-breaking-of-scaling
#7
H George E Hentschel, Prabhat K Jaiswal, Chandana Mondal, Itamar Procaccia, Jacques Zylberg
We revisit the problem of the stress distribution in a frictional sandpile with both normal and tangential (frictional) inter-granular forces, under gravity, equipped with a new numerical method of generating such assemblies. Numerical simulations allow a determination of the spatial dependence of all the components of the stress field, principle stress axis, angle of repose, as a function of systems size, the coefficient of static friction and the frictional interaction with the bottom surface. We compare these results with the predictions of a theory based on continuum equilibrium mechanics...
June 26, 2017: Soft Matter
https://www.readbyqxmd.com/read/28649969/physics-of-muscle-contraction
#8
Matthieu Caruel, Lev Truskinovsky
We present an overview of the recent attempts to complement the chemistry-centered microscopic models of skeletal muscles by the purely mechanical models. The force generation phenomena of interest can be divided into two classes and their mechanisms are usually modeled in dierent ways. Models in the rst class deal with fast force recovery, which does not require detachment of myosin crossbridges and is believed to be a passive process. It can be viewed as collective folding in the system of interacting bi-stable units and is modeled by equilibrium statistical mechanics and Langevin kinetics...
June 26, 2017: Reports on Progress in Physics
https://www.readbyqxmd.com/read/28649828/dimerization-of-the-conserved-n-terminal-domain-of-a-spider-silk-protein-controls-the-self-assembly-of-the-repetitive-core-domain
#9
Joschka Bauer, Thomas Scheibel
Spider silk proteins comprise a repetitive core domain with polyalanine and glycine/proline stretches flanked by highly conserved nonrepetitive N- and C-terminal domains. The termini are responsive to assembly triggers, sensing changes in the ionic (H+, phosphate) and mechanical (shear stress) environment along the spinning duct. Upon assembly, the N-terminal domain dimerizes in a pH-dependent manner induced by protonation of conserved acidic residues. So far, dimerization of N-terminal spider silk domains has been individually investigated in the absence of large core domains...
June 26, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28649330/dual-tracer-based-isotope-turnover-rates-in-a-highly-invasive-mysid-limnomysis-benedeni-from-lake-constance
#10
Elizabeth Yohannes, Karl-Otto Rothhaupt
Understanding the ecological patterns of invasive species and their habitats require an understanding of the species' foraging ecology. Stable carbon (δ(13)C) and nitrogen (δ(15)N) isotope values provide useful information into the study of animal ecology and evolution, since the isotope ratios of consumers reflect consumer's dietary patterns. Nevertheless, the lack of species- and element-specific laboratory-derived turnover rates could limit their application. Using a laboratory-based dual stable isotope tracer approach (Na(15) NO 3 and NaH(13) CO 3), we evaluated the δ(15)N and δ(13)C isotope turnover rates in full-grown adult invasive Limnomysis benedeni from Lake Constance...
June 2017: Ecology and Evolution
https://www.readbyqxmd.com/read/28648547/investigations-on-phosphorus-recovery-from-aqueous-solutions-by-biochars-derived-from-magnesium-pretreated-cypress-sawdust
#11
Khouloud Haddad, Salah Jellali, Mejdi Jeguirim, Aida Ben Hassen Trabelsi, Lionel Limousy
The ability of biochars, derived from the pyrolysis at 400 °C; 500 °C and 600 °C of pretreated cypress sawdust with 20 wt% magnesium chloride (MgCl2) solutions, in recovering phosphorus from aqueous solutions was investigated under various experimental conditions in batch mode. The experimental results indicated that cypress sawdust pretreatment with MgCl2 induced important modifications of the physical and chemical biochars' properties favoring phosphorus recovery from the used synthetic solutions. Moreover, phosphorus recovery efficiency increased with the increase of the used pyrolysis temperature...
June 22, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28648436/angiotensin-converting-enzyme-inhibitors-and-receptor-blockers-in-heart-failure-and-chronic-kidney-disease-demystifying-controversies
#12
REVIEW
Kader Muneer, Anishkumar Nair
In clinical setting, congestive heart failure (CHF) and chronic kidney disease (CKD) often co-exist in patients due to common underlying predisposing factors. An intricate equilibrium between the cardiovascular and renal system is maintained through rennin angiotensin-aldosterone axis and autonomic nervous system. Consequent to favorable hemodynamic modification, angiotensin converting enzyme inhibitors (ACEI) and angiotensin receptor blocking (ARB) therapy have proven to be an indispensable aspect of heart failure management with morbidity and mortality benefit...
May 2017: Indian Heart Journal
https://www.readbyqxmd.com/read/28648060/synthesis-and-spectroscopy-of-silver-doped-pbse-quantum-dots
#13
Daniel M Kroupa, Barbara K Hughes, Elisa M Miller, David T Moore, Nicholas C Anderson, Boris D Chernomordik, Arthur J Nozik, Matthew C Beard
Electronic impurity doping of bulk semiconductors is an essential component of semiconductor science and technology. Yet there are only a handful of studies demonstrating control of electronic impurities in semiconductor nanocrystals. Here, we studied electronic impurity doping of colloidal PbSe quantum dots (QDs) using a postsynthetic cation exchange reaction in which Pb2+ cations are exchanged for Ag+ cations. We found that varying the concentration of dopant ions exposed to the as-synthesized PbSe QDs controls the extent of exchange...
June 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28648046/a-printed-equilibrium-dialysis-device-with-integrated-membranes-for-improved-binding-affinity-measurements
#14
Cody Pinger, Andrew Heller, Dana M Spence
Equilibrium dialysis is a simple and effective technique used for investigating the binding of small molecules and ions to proteins. A 3D-printer was used to create a device capable of measuring binding constants between a protein and a small ion based on equilibrium-dialysis. Specifically, the technology described here enables the user to customize an equilibrium dialysis device to fit their own experiments by choosing membranes of various material and molecular-weight cutoff values. The device has dimensions similar to that of a standard 96-well plate, thus being amenable to automated sample handlers and multi-channel pipettes...
June 25, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28647345/cutaneous-nod2-expression-regulates-the-skin-microbiome-and-wound-healing-in-a-murine-model
#15
Helen Williams, Rachel A Crompton, Helen A Thomason, Laura Campbell, Gurdeep Singh, Andrew J McBain, Sheena M Cruickshank, Matthew J Hardman
The skin microbiome exists in dynamic equilibrium with the host but when the skin is compromised, bacteria can colonise the wound and impair wound healing. Thus the interplay between normal skin-microbial interactions versus pathogenic-microbial interactions in wound repair is important. Bacteria are recognised by innate host pattern recognition receptors (PRRs) and we previously demonstrated an important role for the PRR NOD2 (nucleotide-binding oligomerisation domains-containing protein 2) in skin wound repair...
June 21, 2017: Journal of Investigative Dermatology
https://www.readbyqxmd.com/read/28647285/contrasting-patterns-of-energy-metabolism-in-northern-vs-southern-peripheral-european-flounder-populations-exposed-to-temperature-rising-and-hypoxia
#16
Nicolas Pédron, Jessy Le Du, Grégory Charrier, José-Luis Zambonino-Infante, Nicolas Le Bayon, Rita P Vasconcelos, Vanessa F Fonseca, Fabienne Le Grand, Jean Laroche
A two months common garden experiment was carried out to explore the potential differences of energy metabolism in northern core (France, 50°N and 47°N) vs southern peripheral (Portugal, 41°N) populations of European flounder Platichthys flesus, submitted to cold condition (CC: water temperature = 10 °C) and to warm and hypoxic condition (WHC: water temperature = 22 °C, and moderate hypoxia with O2 saturation = 40% during the last 6 days). Convergent growth rates (in length) were observed in the different populations and conditions, when the southern peripheral population of Portugal did not grow under cold conditions...
June 15, 2017: Marine Environmental Research
https://www.readbyqxmd.com/read/28647261/removal-of-ammonium-ion-from-water-by-na-rich-birnessite-performance-and-mechanisms
#17
Ya Cheng, Tinglin Huang, Xinxin Shi, Gang Wen, Yuankui Sun
Na-rich birnessite (NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion (NH4(+)) from aqueous solution. In order to demonstrate the adsorption performance of the synthesized material, the effects of contact time, pH, initial ammonium ion concentration, and temperature were investigated. Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated...
July 2017: Journal of Environmental Sciences (China)
https://www.readbyqxmd.com/read/28647238/adsorption-desorption-behavior-of-atrazine-on-agricultural-soils-in-china
#18
Lin Yue, ChengJun Ge, Dan Feng, Huamei Yu, Hui Deng, Bomin Fu
Adsorption and desorption are important processes that affect atrazine transport, transformation, and bioavailability in soils. In this study, the adsorption-desorption characteristics of atrazine in three soils (laterite, paddy soil and alluvial soil) were evaluated using the batch equilibrium method. The results showed that the kinetics of atrazine in soils was completed in two steps: a "fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model. In addition, the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models...
July 2017: Journal of Environmental Sciences (China)
https://www.readbyqxmd.com/read/28646673/quantification-of-evaporation-induced-error-in-atom-probe-tomography-using-molecular-dynamics-simulation
#19
Shu Jian Chen, Xupei Yao, Changxi Zheng, Wen Hui Duan
Non-equilibrium molecular dynamics was used to simulate the dynamics of atoms at the atom probe surface and five objective functions were used to quantify errors. The results suggested that before ionization, thermal vibration and collision caused the atoms to displace up to 1Å and 25Å respectively. The average atom displacements were found to vary between 0.2 and 0.5Å. About 9 to 17% of the atoms were affected by collision. Due to the effects of collision and ion-ion repulsion, the back-calculated positions were on average 0...
June 12, 2017: Ultramicroscopy
https://www.readbyqxmd.com/read/28646311/removal-of-arsenic-iii-v-by-a-granular-mn-oxide-doped-al-oxide-adsorbent-surface-characterization-and-performance
#20
Kun Wu, Jin Zhang, Bing Chang, Ting Liu, Furong Zhang, Pengkang Jin, Wendong Wang, Xiaochang Wang
In order to remove arsenic (As) from contaminated water, granular Mn-oxide-doped Al oxide (GMAO) was fabricated using the compression method with the addition of organic binder. The analysis results of XRD, SEM, and BET indicated that GMAO was microporous with a large specific surface area of 54.26 m(2/)g, and it was formed through the aggregation of massive Al/Mn oxide nanoparticles with an amorphous pattern. EDX, mapping, FTIR, and XPS results showed the uniform distribution of Al/Mn elements and numerous hydroxyl groups on the adsorbent surface...
June 23, 2017: Environmental Science and Pollution Research International
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