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https://www.readbyqxmd.com/read/27922069/formation-mechanism-of-ruddlesden-popper-type-antiphase-boundaries-during-the-kinetically-limited-growth-of-sr-rich-srtio3-thin-films
#1
Chencheng Xu, Hongchu Du, Alexander J H van der Torren, Jan Aarts, Chun-Lin Jia, Regina Dittmann
We elucidated the formation process for Ruddlesden-Popper-type defects during pulsed laser deposition of Sr rich SrTiO3 thin films by a combined analysis of in-situ atomic force microscopy, low energy electron diffraction and high resolution scanning transmission electron microscopy. At the early growth stage of 1.5 unit cells, the excess Sr results in the formation of SrO on the surface, resulting in a local termination change from TiO2 to SrO, thereby forming a Sr rich (2 × 2) surface reconstruction...
December 6, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27921368/competing-mechanisms-in-the-acetaldehyde-functionalization-of-positively-charged-hydrogenated-silicene
#2
Li-Kun Yang, Xia-Guang Zhang, Fang-Zu Yang, De-Yin Wu, Zhong-Qun Tian, Xiang-Yang Liu
Density functional theory calculations have been used to elucidate the mechanism of the addition reaction of acetaldehyde to the positively charged hydrogenated silicene (H-silicene). We find that the positively charged H-silicene plane could be partially restructured to form a vacant Si site, enabling a further nucleophilic addition reaction. After acetaldehyde molecule attached to the H-silicene plane, two competing pathways are involved in hydrogen abstraction process: a random reaction mechanism and a chain reaction mechanism...
December 6, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/27920900/polyelectrolyte-coating-on-superparamagnetic-iron-oxide-nanoparticles-as-interface-between-magnetic-core-and-biorelevant-media
#3
Etelka Tombácz, Katalin Farkas, Imre Földesi, Márta Szekeres, Erzsébet Illés, Ildikó Y Tóth, Daniel Nesztor, Tamás Szabó
Nanoparticles do not exist in thermodynamical equilibrium because of high surface free energy, thus they have only kinetic stability. Spontaneous changes can be delayed by designed surface coating. In biomedical applications, superparamagnetic iron oxide nanoparticles (SPIONs) require an optimized coating in order to fulfil the expectation of medicine regulatory agencies and ultimately that of biocompatibility. In this work, we show the high surface reactivity of naked SPIONs due to ≡Fe-OH sites, which can react with H(+)/OH(-) to form pH- and ionic strength-dependent charges...
December 6, 2016: Interface Focus
https://www.readbyqxmd.com/read/27920897/impact-of-biopolymer-matrices-on-relaxometric-properties-of-contrast-agents
#4
Alfonso Maria Ponsiglione, Maria Russo, Paolo Antonio Netti, Enza Torino
Properties of water molecules at the interface between contrast agents (CAs) for magnetic resonance imaging and macromolecules could have a valuable impact on the effectiveness of metal chelates. Recent studies, indeed, demonstrated that polymer architectures could influence CAs' relaxivity by modifying the correlation times of the metal chelate. However, an understanding of the physico-chemical properties of polymer/CA systems is necessary to improve the efficiency of clinically used CAs, still exhibiting low relaxivity...
December 6, 2016: Interface Focus
https://www.readbyqxmd.com/read/27919817/selective-adsorption-of-cr-vi-ions-from-aqueous-solutions-using-cr-6-imprinted-pebax-chitosan-go-aptes-nanofibrous-adsorbent
#5
Mohammadmahdi Etemadi, Saman Samadi, Shabnam Sharif Yazd, Pooya Jafari, Negin Yousefi, Majid Aliabadi
In the present study, a novel Cr(6+)-imprinted Pebax/chitosan/GO/APTES nanofibrous adsorbent (Cr(6+)-PCGA) was prepared and its performance was compared with PCGA nanofibers for selective sorption of Cr(VI) ions from aqueous solutions. The prepared nanofibers were characterized using FTIR, SEM and EDAX analysis. The influence of batch sorption experiments including GO/APTES content, pH, contact time, Cr(VI) initial concentration and temperature on the Cr(VI) sorption efficiency using synthesized nanofibers was investigated...
December 2, 2016: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/27919519/investigation-of-the-acid-base-and-electromigration-properties-of-5-azacytosine-derivatives-using-capillary-electrophoresis-and-density-functional-theory-calculations
#6
Denisa Geffertová, Syed Tahir Ali, Veronika Šolínová, Marcela Krečmerová, Antonín Holý, Zdeněk Havlas, Václav Kašička
Capillary electrophoresis (CE) and quantum mechanical density functional theory (DFT) were applied to the investigation of the acid-base and electromigration properties of important compounds: newly synthesized derivatives of 5-azacytosine - analogs of efficient antiviral drug cidofovir. These compounds exhibit a strong antiviral activity and they are considered as potential new antiviral agents. For their characterization and application, it is necessary to know their acid-base properties, particularly the acidity constants (pKa) of their ionogenic groups (the basic N(3) atom of the triazine ring and the acidic phosphonic acid group in the alkyl chain)...
November 29, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/27918986/hybrid-chitosan-polyaniline-polypyrrole-biomaterial-for-enhanced-adsorption-and-antimicrobial-activity
#7
Rajeev Kumar, Mohammad Oves, Talla Ameelbi, Naief H Al-Makishah, M A Barakat
In this work, chitosan (CS) functionalized polyaniline-polypyrrole (Pani-Ppy) copolymer (CS/Pani-Ppy) was synthesized applying a facile one pot method for the enhanced adsorption of Zn(II) and antimicrobial activity for E. coli and E. agglomerans. The synthesized materials were characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform inferred spectroscopy and X-ray photoelectron spectroscopy. The adsorption of the Zn(II) on the synthesized materials was highly dependent on the pH of the solution, the initial metal ion concentration, and temperature...
November 24, 2016: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/27918617/thermodynamic-insights-on-a-bistable-acid-base-switchable-molecular-shuttle-with-strongly-shifted-co-conformational-equilibria
#8
Giulio Ragazzon, Alberto Credi, Benoit Colasson
Bistable [2]rotaxanes in which the affinities of the two stations can be reversed form the basis of molecular shuttles. Gaining quantitative information on such rotaxanes in which the ring distribution between the two stations is largely nonsymmetric has proven to be very challenging. Here we report on two independent experimental methodologies - based on luminescence lifetime measurement and acid-base titrations - to determine the relative populations of the two co-conformations of a [2]rotaxane. The assays yield convergent results and are sensitive enough to measure an equilibrium constant (K ~ 4000) out of reach for NMR spectroscopy...
December 5, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27917865/critical-exponents-and-scaling-invariance-in-the-absence-of-a-critical-point
#9
N Saratz, D A Zanin, U Ramsperger, S Cannas, D Pescia, A Vindigni
The paramagnetic-to-ferromagnetic phase transition is classified as a critical phenomenon due to the power-law behaviour shown by thermodynamic observables when the Curie point is approached. Here we report the observation of such a behaviour over extraordinarily many decades of suitable scaling variables in ultrathin Fe films, for certain ranges of temperature T and applied field B. This despite the fact that the underlying critical point is practically unreachable because protected by a phase with a modulated domain structure, induced by the dipole-dipole interaction...
December 5, 2016: Nature Communications
https://www.readbyqxmd.com/read/27916693/comparison-of-2-strategies-to-enhance-pyridoclax-solubility-nanoemulsion-delivery-system-versus-salt-synthesis
#10
A-C Groo, M De Pascale, A-S Voisin-Chiret, S Corvaisier, M Since, A Malzert-Fréon
Pyridoclax is an original oligopyridine lead, very promising in treatment of chemoresistant cancers. However, from solubility measurement and permeability evaluation, it appeared that this compound can be considered as a BCS II drug, with a poor water solubility. To overcome this unfavorable property, two strategies were proposed and compared: pyridoclax di-hydrochloride salt synthesis and formulation of pyridoclax-loaded nanoemulsions (PNEs) efficiently performed by transposing the spontaneous emulsification process previously developed by our team...
December 1, 2016: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/27916639/binding-thermodynamics-discriminates-fragments-from-druglike-compounds-a-thermodynamic-description-of-fragment-based-drug-discovery
#11
REVIEW
Glyn Williams, György G Ferenczy, Johan Ulander, György M Keserű
Small is beautiful - reducing the size and complexity of chemical starting points for drug design allows better sampling of chemical space, reveals the most energetically important interactions within protein-binding sites and can lead to improvements in the physicochemical properties of the final drug. The impact of fragment-based drug discovery (FBDD) on recent drug discovery projects and our improved knowledge of the structural and thermodynamic details of ligand binding has prompted us to explore the relationships between ligand-binding thermodynamics and FBDD...
December 1, 2016: Drug Discovery Today
https://www.readbyqxmd.com/read/27915407/analysis-of-the-antioxidant-activity-of-4-5-chloro-2-hydroxyphenylamino-4-oxobut-2-enoic-acid-derivatives-using-quantum-chemistry-descriptors-and-molecular-docking
#12
Ahmed Taki Eddine Ardjani, Sidi Mohamed Mekelleche
In the present work, the molecular structure and the antioxidant activity of 4-(5-chloro-2-hydroxyphenylamino)-4-oxobut-2-enoic acid (A) and its derivatives (B-E) have been studied at the B3LYP/6-31++G(2d,2p) computational level. The obtained results indicate that the hydrogen atom transfer (HAT mechanism) is thermodynamically more favored in gas phase; whereas, the sequential proton loss-electron transfer (SPLET mechanism) is more preferred in polar solvents. The antioxidant activity of compounds A-E is also analyzed by the calculation of atomic spin densities, chemical hardnesses, dipole moments, and lipophilicity indexes...
December 2016: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/27915305/dna-barcoding-coupled-with-high-resolution-melting-analysis-enables-rapid-and-accurate-distinction-of-aspergillus-species
#13
Gabor Fidler, Sandor Kocsube, Eva Leiter, Sandor Biro, Melinda Paholcsek
We describe a high-resolution melting (HRM) analysis method that is rapid, reproducible, and able to identify reference strains and further 40 clinical isolates of Aspergillus fumigatus (14), A. lentulus (3), A. terreus (7), A. flavus (8), A. niger (2), A. welwitschiae (4), and A. tubingensis (2). Asp1 and Asp2 primer sets were designed to amplify partial sequences of the Aspergillus benA (beta-tubulin) genes in a closed-, single-tube system. Human placenta DNA, further Aspergillus (3), Candida (9), Fusarium (6), and Scedosporium (2) nucleic acids from type strains and clinical isolates were also included in this study to evaluate cross reactivity with other relevant pathogens causing invasive fungal infections...
December 3, 2016: Medical Mycology: Official Publication of the International Society for Human and Animal Mycology
https://www.readbyqxmd.com/read/27915145/co-adsorption-of-perfluorooctane-sulfonate-and-phosphate-on-boehmite-influence-of-temperature-phosphate-initial-concentration-and-ph
#14
Jin Qian, Mengmeng Shen, Peifang Wang, Chao Wang, Jing Hu, Jun Hou, Yanhui Ao, Hao Zheng, Kun Li, Jingjing Liu
The co-presence of perfluorooctane sulfonate (PFOS) and phosphate in wastewater of various industries has been detected. Removing PFOS and phosphate simultaneously before discharging sewage into natural water can decrease effectively the environmental risk caused by the combined pollution of PFOS and phosphate. In this study, laboratory batch experiments were conducted for investigating the co-adsorption of PFOS and phosphate on boehmite and the influences of temperature, phosphate initial concentration and pH on the co-adsorption...
December 1, 2016: Ecotoxicology and Environmental Safety
https://www.readbyqxmd.com/read/27915045/in-vivo-selection-of-heterotypically-interacting-transmembrane-helices-complementary-helix-surfaces-rather-than-conserved-interaction-motifs-drive-formation-of-transmembrane-hetero-dimers
#15
Dominik Steindorf, Dirk Schneider
Single pass transmembrane proteins make up almost half of the whole transmembrane proteome. Contacts between such bitopic transmembrane proteins are common, and oligomerization of their single transmembrane helix is involved in triggering and regulation of signal transduction across cell membranes. In several recent analyses the distribution of amino acids at helix-helix contact sides has been analyzed, and e.g. a preference of amino acids with small side chains has been identified. Here we select amino acids, amino acid pairings and amino acid motifs, which mediate strong interactions of single-span transmembrane α-helices...
November 30, 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27914253/protein-conjugation-with-pamam-nanoparticles-microscopic-and-thermodynamic-analysis
#16
P Chanphai, E Froehlich, J S Mandeville, H A Tajmir-Riahi
PAMAM dendrimers form strong protein conjugates that are used in drug delivery systems. We report the thermodynamic and binding analysis of polyamidoamine (PAMAM-G4) conjugation with human serum albumin (HSA), bovine serum albumin (BSA) and milk beta-lactoglobulin (b-LG) in aqueous solution at physiological pH. Hydrophobicity played a major role in PAMAM-protein interactions with more hydrophobic b-LG forming stronger polymer-protein conjugates. Thermodynamic parameters showed PAMAM-protein bindings occur via hydrophobic and H-bonding contacts for b-LG, while van der waals and H-bonding interactions prevail in HSA and BSA-polymer conjugates...
November 27, 2016: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/27914048/geometric-potentials-for-computational-protein-sequence-design
#17
Jie Li, Patrice Koehl
Computational protein sequence design is the rational design based on computer simulation of new protein molecules to fold to target three-dimensional structures, with the ultimate goal of designing novel functions. It requires a good understanding of the thermodynamic equilibrium properties of the protein of interest. Here, we consider the contribution of the solvent to the stability of the protein. We describe implicit solvent models, focusing on approximations of their nonpolar components using geometric potentials...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/27914004/hybrid-receptor-bound-mm-gbsa-per-residue-energy-based-pharmacophore-modelling-enhanced-approach-for-identification-of-selective-lta4h-inhibitors-as-potential-anti-inflammatory-drugs
#18
Patrick Appiah-Kubi, Mahmoud Soliman
Leukotriene A4 hydrolase has been identified as an enzyme with dual anti- and pro-inflammatory role, thus, the conversion of leukotriene to leukotriene B4 in the initiation stage of inflammation and the removal of the chemotactic Pro-Gly-Pro tripeptide. These findings make leukotriene A4 hydrolase an attractive drug target: suggesting an innovative approach towards the identification and design of novel class of compounds that can selectively inhibit leukotriene B4 synthesis while sparing the aminopeptidase activity...
December 2, 2016: Cell Biochemistry and Biophysics
https://www.readbyqxmd.com/read/27913731/disentangling-polydispersity-in-the-pcna-p15paf-complex-a-disordered-transient-and-multivalent-macromolecular-assembly
#19
Tiago N Cordeiro, Po-Chia Chen, Alfredo De Biasio, Nathalie Sibille, Francisco J Blanco, Jochen S Hub, Ramon Crehuet, Pau Bernadó
The intrinsically disordered p15(PAF) regulates DNA replication and repair when interacting with the Proliferating Cell Nuclear Antigen (PCNA) sliding clamp. As many interactions between disordered proteins and globular partners involved in signaling and regulation, the complex between p15(PAF) and trimeric PCNA is of low affinity, forming a transient complex that is difficult to characterize at a structural level due to its inherent polydispersity. We have determined the structure, conformational fluctuations, and relative population of the five species that coexist in solution by combining small-angle X-ray scattering (SAXS) with molecular modelling...
December 1, 2016: Nucleic Acids Research
https://www.readbyqxmd.com/read/27913058/effect-of-urea-on-protein-ligand-association
#20
Lora Stepanian, Ikbae Son, Tigran V Chalikian
We combine experimental and theoretical approaches to investigate the influence of a cosolvent on a ligand-protein association event. We apply fluorescence measurements to determining the affinity of the inhibitor tri-N-acetylglucosamine [(GlcNAc)3] for lysozyme at urea concentrations ranging from 0 to 8M. Notwithstanding that, at room temperature and neutral pH, lysozyme retains its native conformation up to the solubility limit of urea, the affinity of (GlcNAc)3 for the protein steadily decreases as the concentration of urea increases...
November 25, 2016: Biophysical Chemistry
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