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https://www.readbyqxmd.com/read/29166119/two-phase-thermodynamic-model-for-computing-entropies-of-liquids-reanalyzed
#1
Tao Sun, Jiawei Xian, Huai Zhang, Zhigang Zhang, Yigang Zhang
The two-phase thermodynamic (2PT) model [S.-T. Lin et al., J. Chem. Phys. 119, 11792-11805 (2003)] provides a promising paradigm to efficiently determine the ionic entropies of liquids from molecular dynamics. In this model, the vibrational density of states (VDoS) of a liquid is decomposed into a diffusive gas-like component and a vibrational solid-like component. By treating the diffusive component as hard sphere (HS) gas and the vibrational component as harmonic oscillators, the ionic entropy of the liquid is determined...
November 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29166107/simulations-of-water-nano-confined-between-corrugated-planes
#2
Jon Zubeltzu, Emilio Artacho
Water confined to nanoscale widths in two dimensions between ideal planar walls has been the subject of ample study, aiming at understanding the intrinsic response of water to confinement, avoiding the consideration of the chemistry of actual confining materials. In this work, we study the response of such nanoconfined water to the imposition of a periodicity in the confinement by means of computer simulations, both using empirical potentials and from first-principles. For that we propose a periodic confining potential emulating the atomistic oscillation of the confining walls, which allows varying the lattice parameter and amplitude of the oscillation...
November 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29166032/combined-cononsolvency-and-temperature-effects-on-adsorbed-pnipam-microgels
#3
Sebastian Backes, Patrick Krause, Weronika Tabaka, Marcus U Witt, Regine von Klitzing
The present study adresses the multi-responsive behavior of Poly(N-isopropylacrylamide) (PNIPAM) microgels adsorbed to interfaces. The microgels react to changes in temperature by shrinking in aqueous solution above their volume phase transition temperature (VPTT). Additionally, they shrink in mixtures of water and ethanol, although both individual liquids are good solvents for PNIPAM. The combination of this so-called cononsolvency effect and the temperature response of adsorbed microgels is studied by atomic force microscopy (AFM)...
November 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29164764/influence-of-levulinic-acid-hydrogenation-on-aluminum-coordination-in-zeolite-supported-ruthenium-catalysts-a%C3%A2-27-al-3qmas-nuclear-magnetic-resonance-study
#4
Wenhao Luo, Ernst R H van Eck, Pieter C A Bruijnincx, Bert M Weckhuysen
The influence of a highly oxygenated, polar protic reaction medium, that is, levulinic acid in 2-ethylhexanoic acid, on the dealumination of two zeolite-supported ruthenium catalysts, namely Ru/H-β and Ru/H-ZSM-5, has been investigated by (27) Al triple-quantum magic-angle spinning nuclear magnetic resonance spectroscopy (3QMAS NMR). Upon use of these catalysts in the hydrogenation of levulinic acid, the heterogeneity in aluminum speciation is found to increase for both Ru/H-ZSM-5 and Ru/H-β. For Ru/H-ZSM-5, the symmetric, tetrahedral framework aluminum species (FAL) were found to be mainly converted into distorted tetrahedral FAL species, with limited loss of aluminum to the solution by leaching...
November 22, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/29161962/purification-and-structural-analysis-of-volatile-sesquiterpenes-produced-by-escherichia-coli-carrying-unidentified-terpene-synthase-genes-from-edible-plants-of-the-family-araliaceae
#5
Kazutoshi Shindo, Jun-Ichiro Hattan, Mariko Kato, Miho Sato, Tomoko Ito, Yurika Shibuya, Arisa Watanabe, Maki Sugiyama, Yuri Nakamura, Norihiko Misawa
A simple method to purify volatile sesquiterpenes from recombinant Escherichia coli was developed using the cells that carried known sesquiterpene synthase (Tps) genes ZzZss2 (ZSS2) and ZoTps1. This method was applied for the purification and structural analyses of volatile sesquiterpenes produced by E. coli cells that carried unidentified Tps genes, which were isolated from the Aralia-genus edible plants belonging to the family Araliaceae. Recombinant cells carrying each Tps gene were cultured in the two-layer medium (n-octane/TB medium), and volatile sesquiterpenes trapped in n-octane were purified through two-phase partition, silica gel column chromatography, and reversed-phase preparative high-performance liquid chromatography, if necessary...
November 22, 2017: Bioscience, Biotechnology, and Biochemistry
https://www.readbyqxmd.com/read/29158663/a-comparative-pharmacokinetic-and-tolerability-analysis-of-the-novel-orotic-acid-salt-form-of-tenofovir-disoproxil-and-the-fumaric-acid-salt-form-in-healthy-subjects
#6
Yu Kyong Kim, Mun Ju Choi, Tae Young Oh, Kyung-Sang Yu, SeungHwan Lee
A novel orotic acid salt form of tenofovir disoproxil (DA-2802) was developed and is expected to replace the fumaric acid salt form. The pharmacokinetic (PK) characteristics and tolerability profiles of DA-2802 were compared to those of tenofovir disoproxil fumarate (TDF, Viread(®)) in healthy subjects. A randomized, open-label, single-dose study was conducted in 36 healthy subjects using a two-treatment, two-period, and two-sequence crossover design. Subjects received a single oral dose of 319 mg DA-2802 or 300 mg TDF, during each period, with a 7-day washout...
2017: Drug Design, Development and Therapy
https://www.readbyqxmd.com/read/29156265/occurrence-and-fate-of-most-prescribed-antibiotics-in-different-water-environments-of-tehran-iran
#7
Roya Mirzaei, Masud Yunesian, Simin Nasseri, Mitra Gholami, Esfandiyar Jalilzadeh, Shahram Shoeibi, Alireza Mesdaghinia
The presence of most prescribed antibiotic compounds from four therapeutic classes (β-lactam, cephalosporins, macrolides, fluoroquinolones) were studied at two full-scale WWTPs, two rivers, thirteen groundwater resources, and five water treatment plants in Tehran. Analytical methodology was based on high performance liquid chromatography/tandem mass spectrometry after solid-phase extraction. Samples were collected at 33 sample locations on three sampling periods over four months from June to August 2016. None of the target antibiotics were detected in groundwater resources and water treatment plants, while seven out of nine target antibiotics were analyzed in two studied river waters as well as the influent and effluent of wastewater treatment plants at concentrations ranging from <LOQ to 926...
November 16, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29155739/standardized-method-for-high-throughput-sterilization-of-arabidopsis-seeds
#8
Benson E Lindsey, Luz Rivero, Chistopher S Calhoun, Erich Grotewold, Jelena Brkljacic
Arabidopsis thaliana (Arabidopsis) seedlings often need to be grown on sterile media. This requires prior seed sterilization to prevent the growth of microbial contaminants present on the seed surface. Currently, Arabidopsis seeds are sterilized using two distinct sterilization techniques in conditions that differ slightly between labs and have not been standardized, often resulting in only partially effective sterilization or in excessive seed mortality. Most of these methods are also not easily scalable to a large number of seed lines of diverse genotypes...
October 17, 2017: Journal of Visualized Experiments: JoVE
https://www.readbyqxmd.com/read/29154196/analysis-of-potential-genotoxic-impurities-in-rabeprazole-active-pharmaceutical-ingredient-via-liquid-chromatography-tandem-mass-spectrometry-following-quality-by-design-principles-for-method-development
#9
Katerina Iliou, Anđelija Malenović, Yannis L Loukas, Yannis Dotsikas
A novel Liquid Chromatography-tandem mass spectrometry (LC-MS/MS) method is presented for the quantitative determination of two potential genotoxic impurities (PGIs) in rabeprazole active pharmaceutical ingredient (API). In order to overcome the analytical challenges in the trace analysis of PGIs, a development procedure supported by Quality-by-Design (QbD) principles was evaluated. The efficient separation between rabeprazole and the two PGIs in the shortest analysis time was set as the defined analytical target profile (ATP) and to this purpose utilization of a switching valve allowed the flow to be sent to waste when rabeprazole was eluted...
November 12, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/29152974/biocompatible-copper-oxide-nanoparticle-composites-from-cellulose-and-chitosan-facile-synthesis-unique-structure-and-antimicrobial-activity
#10
Chieu D Tran, James Makuvaza, Erik Munson, Brian Bennett
Copper in various forms has been known to have bactericidal activity. Challenges to its application include preventing mobilization of the copper, to both extend activity and avoid toxicity, and bioincompatibility of many candidate substrates for copper-immobilization. Using a simple ionic liquid, butylmethylimmidazolium chloride as the solvent, we developed a facile and green method to synthesize biocompatible composites containing copper oxide nanoparticles (CuONPs) from cellulose (CEL) and chitosan (CS) or CEL and keratin (KER)...
November 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29152634/effects-of-ionic-liquids-on-the-nanoscopic-dynamics-and-phase-behaviour-of-a-phosphatidylcholine-membrane
#11
V K Sharma, S K Ghosh, P Mandal, T Yamada, K Shibata, S Mitra, R Mukhopadhyay
Ionic liquids (ILs) are potential candidates for new antimicrobials due to their tunable antibacterial and antifungal properties that are required to keep pace with the growing challenge of bacterial resistance. To a great extent their antimicrobial actions are related to the interactions of ILs with cell membranes. Here, we report the effects of ILs on the nanoscopic dynamics and phase behaviour of a dimyristoylphosphatidylcholine (DMPC) membrane, a model cell membrane, as studied using neutron scattering techniques...
November 20, 2017: Soft Matter
https://www.readbyqxmd.com/read/29150928/application-of-high-speed-counter-current-chromatography-and-hplc-to-separate-and-purify-of-three-polyacetylenes-from-platycodon-grandiflorum
#12
Bao Chen, Zhengbo Liu, Yuwei Zhang, Wei Li, Yanjun Sun, Yufang Wang, Yanhua Wang, Yinshi Sun
Three polyacetylenes were isolated and purified from Platycodon grandiflorum A. DC for the first time by high-speed counter-current chromatography using a two-phase solvent system composed of hexane/ethyl acetate/methanol/water (1:31:1:31, v/v/v/v) and high-performance liquid chromatography with an Agilent ZORBAX(®) SB-C18 column (4.6 mm × 150 mm, 5 μm). After separation by high-speed counter-current chromatography and high-performance liquid chromatography, we obtained 3.5 mg of platetyolin A, 4.1 mg of platetyolin B, and 18...
November 18, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/29149996/coupling-of-two-centrifugeless-ultrasound-assisted-dispersive-solid-liquid-phase-microextractions-as-a-highly-selective-clean-and-efficient-method-for-determination-of-ultra-trace-amounts-of-non-steroidal-anti-inflammatory-drugs-in-complicated-matrices
#13
Somayeh Arghavani-Beydokhti, Maryam Rajabi, Alireza Asghari
In this work, a new, simple, rapid, and environmentally friendly method with a high sample clean-up capability termed as centrifugeless ultrasound-assisted dispersive micro solid-phase extraction coupled with salting-out ultrasound-assisted liquid-liquid microextraction based on solidification of a floating organic droplet followed by high performance liquid chromatography is introduced for the first time. In this method, the three non-steroidal anti-inflammatory drugs diclofenac, ibuprofen, and mefenamic acid are first extracted based on an effective nanoadsorbent named as the layered double hydroxide-carbon nanotube nanohybrid...
January 2, 2018: Analytica Chimica Acta
https://www.readbyqxmd.com/read/29149711/enantiomeric-characterization-of-herbicide-lactofen-enantioseparation-absolute-configuration-assignment-and-enantioselective-activity-and-toxicity
#14
Jingqian Xie, Lu Zhao, Kai Liu, Fangjie Guo, Zunwei Chen, Weiping Liu
Chiral herbicides consist of two or more enantiomers, which usually differ in their biological properties and behave enantioselectively in biochemical process. Scant studies have been published in the past decades to characterize the enantiomers of herbicide lactofen. In this study, a laboratory method was developed to prepare the lactofen enantiomers using normal phase high performance liquid chromatography with an AD-H column, and μg level production yield was achieved in a single run. The two separated enantiomers had purity of ≫99%, with their absolute configurations assigned by experimental and calculated electronic and vibrational circular dichroism...
October 31, 2017: Chemosphere
https://www.readbyqxmd.com/read/29149702/an-hplc-tandem-mass-spectrometry-for-quantification-of-et-26-hcl-and-its-major-metabolite-in-plasma-and-application-to-a-pharmacokinetic-study-in-rats
#15
Xu Chen, Wensheng Zhang, Sandy Rios, Miriam B Morkos, Xiaoli Ye, Gen Li, Xuehua Jiang, Zhijun Wang, Ling Wang
ET-26-HCl is a new analog of etomidate, a short-acting anesthetic drug, with less adrenal cortex inhibition. The pharmacokinetics of ET-26-HCl in rats needs to be determined for future clinical trials in human subjects. In order to facilitate the pharmacokinetic study, a liquid chromatography based tandem mass spectrometric (HPLC-MS/MS) method was developed and validated for quantification of ET-26-HCl and its major metabolite, ET-26-acid. These two compounds and gabapentin (internal standard) were extracted using a protein precipitation method with methanol and detected by Multiple Reaction Monitoring of m/z transition of 275...
November 8, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/29148781/compound-stability-in-nano-particles-the-effect-of-solid-phase-fraction-on-diffusion-of-degradation-agents-into-nanostructured-lipid-carriers
#16
Daniel D Nelson, Yuanjie Pan, Rohan V Tikekar, Nily R Dan, N Nitin
The stability of active compounds encapsulated in nanoparticles depends on the resistance of the particles to diffusion of environmental degradation agents. In this paper, off-lattice Monte Carlo simulations are used to investigate a suspension of nanostructured lipid carriers (NLC) composed of interspaced liquid and solid lipid domains, immersed in a solution containing molecules representing oxidative or other degradation agents. The simulations examine the diffusion of the degradation agents into the nanoparticles as a function of nanoparticle size, solid domain fraction, and domain size...
November 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29146427/applicability-of-retention-modelling-in-hydrophilic-interaction-liquid-chromatography-for-algorithmic-optimization-programs-with-gradient-scanning-techniques
#17
Bob W J Pirok, Stef R A Molenaar, Rianne E van Outersterp, Peter J Schoenmakers
Computer-aided method-development programs require accurate models to describe retention and to make predictions based on a limited number of scouting gradients. The performance of five different retention models for hydrophilic-interaction chromatography (HILIC) is assessed for a wide range of analytes. Gradient-elution equations are presented for each model, using Simpson's Rule to approximate the integral in case no exact solution exists. For most compound classes the adsorption model, i.e. a linear relation between the logarithm of the retention factor and the logarithm of the composition, is found to provide the most robust performance...
November 11, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/29146423/comprehensive-lipidomic-analysis-of-human-plasma-using-multidimensional-liquid-and-gas-phase-separations-two-dimensional-liquid-chromatography-mass-spectrometry-vs-liquid-chromatography-trapped-ion-mobility-mass-spectrometry
#18
Anna Baglai, Andrea F G Gargano, Jan Jordens, Ynze Mengerink, Maarten Honing, Sjoerd van der Wal, Peter J Schoenmakers
Recent advancements in separation science have resulted in the commercialization of multidimensional separation systems that provide higher peak capacities and, hence, enable a more-detailed characterization of complex mixtures. In particular, two powerful analytical tools are increasingly used by analytical scientists, namely online comprehensive two-dimensional liquid chromatography (LC×LC, having a second-dimension separation in the liquid phase) and liquid chromatography-ion mobility-spectrometry (LC-IMS, second dimension separation in the gas phase)...
November 10, 2017: Journal of Chromatography. A
https://www.readbyqxmd.com/read/29144423/lipid-peroxidation-process-in-meat-and-meat-products-a-comparison-study-of-malondialdehyde-determination-between-modified-2-thiobarbituric-acid-spectrophotometric-method-and-reverse-phase-high-performance-liquid-chromatography
#19
Anna Reitznerová, Monika Šuleková, Jozef Nagy, Slavomír Marcinčák, Boris Semjon, Milan Čertík, Tatiana Klempová
The aim of this work was to compare the methods of malondialdehyde detection, as the main secondary product of the lipid peroxidation process, in meat and meat products. Malondialdehyde measurements were performed by two modified methods, the 2-thiobarbituric acid spectrophotometric method and the reverse-phase high-performance liquid chromatography in raw, mechanically-deboned chicken meat and in manufactured frankfurters. The malondialdehyde concentrations measured by the 2-thiobarbituric acid spectrophotometric method were found to be overestimated by more than 25% in raw meat and more than 27% in frankfurters in comparison to the results of reverse-phase high-performance liquid chromatography (p < 0...
November 16, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29142260/possible-nematic-to-smectic-phase-transition-in-a-two-dimensional-electron-gas-at-half-filling
#20
Q Qian, J Nakamura, S Fallahi, G C Gardner, M J Manfra
Liquid crystalline phases of matter permeate nature and technology, with examples ranging from cell membranes to liquid-crystal displays. Remarkably, electronic liquid-crystal phases can exist in two-dimensional electron systems (2DES) at half Landau-level filling in the quantum Hall regime. Theory has predicted the existence of a liquid-crystal smectic phase that breaks both rotational and translational symmetries. However, previous experiments in 2DES are most consistent with an anisotropic nematic phase breaking only rotational symmetry...
November 16, 2017: Nature Communications
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