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Physical Chemistry Chemical Physics: PCCP

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https://www.readbyqxmd.com/read/27910984/enzyme-immobilized-clay-nanotube-chitosan-membranes-with-sustainable-biocatalytic-activities
#1
Jiajia Sun, Raghuvara Yendluri, Kai Liu, Ying Guo, Yuri Lvov, Xuehai Yan
We have developed a simple and effective strategy to prepare an enzymatic membrane by the admixing of a halloysite clay nanotube-lipase complex and a chitosan solution. The loading of 3 wt% lipase into the lumen of halloysite clay nanotubes was enhanced with an electrostatic interaction. 10 wt% of lipase-nanotubes were dispersed in an aqueous chitosan solution and cast as a coating. The enzymatic chitosan-halloysite membranes displayed increased pH, temperature stability and long-term usability for the catalytic decomposition of lipids: 90% of the initial activity was preserved at 80 °C, 70% of the functionality remained at the high pH of 9, and 85% of the activity was sustained after ten continuous cycles of use...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27910970/exploration-of-hydrogen-bond-networks-and-potential-energy-surfaces-of-methanol-clusters-using-a-two-stage-clustering-algorithm
#2
Po-Jen Hsu, Kun-Lin Ho, Sheng-Hsien Lin, Jer-Lai Kuo
The potential energy surface (PES), structures and thermal properties of methanol clusters (MeOH)n with n = 8-15 were explored by replica-exchange molecular dynamics (REMD) simulations with an empirical model and refined using density functional theory (DFT) methods. For a given size, local minima structures were sampled from REMD trajectories and archived by a newly developed molecular database via a two-stage clustering algorithm (TSCA). Our TSCA utilizes both the topology of O-HO hydrogen bonding networks and the similarity of the shapes to filter out duplicates...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27910969/the-intramolecular-h-bonding-effect-on-the-growth-and-stability-of-schiff-base-surface-covalent-organic-frameworks
#3
Yi-Ping Mo, Xuan-He Liu, Bing Sun, Hui-Juan Yan, Dong Wang, Li-Jun Wan
The introduction of intramolecular H-bonding by adding -OH functionalities adjacent to the Schiff base centers is considered to be a useful strategy to enhance the stability and crystallinity of bulk covalent organic frameworks (COFs). However, the influence of intramolecular H-bonding on the synthesis of surface COFs (SCOFs) have been barely explored. Herein, SCOFs based on the Schiff-base reaction between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehydes with symmetry or asymmetrically substituted hydroxyl functional groups are designed...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27910968/designing-hierarchical-hollow-nanostructures-of-cu2mos4-for-improved-hydrogen-evolution-reaction
#4
Ke Zhang, Yongli Zheng, Yunxiang Lin, Changda Wang, Hengjie Liu, Daobin Liu, Chuanqiang Wu, Shuangming Chen, Yanxia Chen, Li Song
Layered Cu2MoS4, consisting of earth-abundant elements, is regarded as a potential catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a Cu2O-based template strategy to synthesise hierarchical hollow nanostructures of Cu2MoS4. The characterizations reveal that the electrochemically active surface of the hollow Cu2MoS4 is largely enhanced, in contrast to the nanosheet or nanoparticle structures. As the direct outcome, the designed hierarchical hollow structures display excellent HER activities with a low overvoltage and small Tafel slope...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27906383/an-improved-model-of-homogeneous-nucleation-for-high-supersaturation-conditions-aluminum-vapor
#5
A M Savel'ev, A M Starik
A novel model of stationary nucleation, treating the thermodynamic functions of small clusters, has been built. The model is validated against the experimental data on the nucleation rate of water vapor obtained in a broad range of supersaturation values (S = 10-120), and, at high supersaturation values, it reproduces the experimental data much better than the traditional classical nucleation model. A comprehensive analysis of the nucleation of aluminum vapor with the usage of developed stationary and non-stationary nucleation models has been performed...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905609/pursuing-reliable-thermal-analysis-techniques-for-energetic-materials-decomposition-kinetics-and-thermal-stability-of-dihydroxylammonium-5-5-bistetrazole-1-1-diolate-tkx-50
#6
Nikita V Muravyev, Konstantin A Monogarov, Andrey F Asachenko, Mikhail S Nechaev, Ivan V Ananyev, Igor V Fomenkov, Vitaly G Kiselev, Alla N Pivkina
Thermal decomposition of a novel promising high-performance explosive dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) was studied using a number of thermal analysis techniques (thermogravimetry, differential scanning calorimetry, and accelerating rate calorimetry, ARC). To obtain more comprehensive insight into the kinetics and mechanism of TKX-50 decomposition, a variety of complementary thermoanalytical experiments were performed under various conditions. Non-isothermal and isothermal kinetics were obtained at both atmospheric and low (up to 0...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905608/drop-coating-deposition-of-a-liposome-suspension-on-surfaces-with-different-wettabilities-coffee-ring-formation-and-suspension-preconcentration
#7
Eva Kočišová, Martin Petr, Hana Šípová, Ondřej Kylián, Marek Procházka
Evaporation of a drop of biomolecular solution on a solid surface typically creates a ring-shaped drying pattern, formed by the so-called "coffee ring" effect. The size and shape of the "coffee ring" pattern is strongly dependent on the properties of the surface as well as on the deposited molecular solution or suspension. In this paper, we tested six types of surfaces differing in their physico-chemical surface characteristics (contact angles, wettability and roughness) as well as in the presence or absence of a base metal layer...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905607/a-heat-capacity-model-of-t-3-2-dependence-for-quantum-dots
#8
Amirul Edham Roslee, Saifful Kamaluddin Muzakir, Jamil Ismail, Mashitah M Yusoff, Rajan Jose
This article addresses the heat capacity of quantum dots (QDs) using density functional theory (DFT). By analyzing the evolution of phonon density of states and heat capacity as CdSe clusters grow from a molecular cluster into larger quantum confined solids, we have shown that their heat capacity does not fit very well with the Debye T(3) model. We observed that the number of phonon modes, which is discrete, increases as the particles grow, and the dispersion relation shows a quadratic behavior in contrast to the bulk solids whose dispersion relation is linear and equal to the sound velocity...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905606/a-qm-mm-study-of-the-reaction-mechanism-of-human-%C3%AE-ketoacyl-reductase
#9
Fabiola E Medina, Rui P P Neves, Maria J Ramos, Pedro A Fernandes
Human fatty acid synthase (hFAS) is a multifunctional enzyme involved in a wide diversity of biological functions. For instance, it is a precursor of phospholipids and other complex processes such as the de novo synthesis of long chain fatty acid. Human FAS is also a component of biological membranes and it is implicated in the overexpression of several types of cancers. In this work, we describe the catalytic mechanism of β-ketoreductase (KR), which is a catalytic domain of the hFAS enzyme that catalyzes the reduction of β-ketoacyl to β-hydroxyacyl with the concomitant oxidation of the NADPH cofactor...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905605/an-efficient-2d-11-b-11-b-solid-state-nmr-spectroscopy-strategy-for-monitoring-covalent-self-assembly-of-boronic-acid-derived-compounds-the-transformation-and-unique-architecture-of-bortezomib-molecules-in-the-solid-state
#10
J Brus, J Czernek, M Urbanova, L Kobera, A Jegorov
The difficulty in the prediction of the complicated solid-state structure of boronic acid derivatives, resulting from the complex pathway of reversible covalent interactions, represents a significant obstacle to the development of a new generation of advanced supramolecular systems such as covalent organic frameworks of efficient anticancer drugs. In this contribution, various 2D (11)B-(11)B solid-state NMR correlation techniques supported by DFT calculations were explored to formulate a reliable tool for monitoring the covalent assembly of boronic acid residues in the solid state...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905604/an-experimental-and-theoretical-investigation-of-the-c-1-d-d2-reaction
#11
Kevin M Hickson, Yury V Suleimanov
In a previous joint experimental and theoretical study of the barrierless chemical reaction C((1)D) + H2 at low temperatures (300-50 K) [K. M. Hickson, J.-C. Loison, H. Guo and Y. V. Suleimanov, J. Phys. Chem. Lett., 2015, 6, 4194], excellent agreement was found between experimental thermal rate constants and theoretical estimates based on ring polymer molecular dynamics (RPMD) over the two lowest singlet potential energy surfaces (PESs). Here, we extend this work to one of its isotopologues, C((1)D) + D2, over the same temperature range...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905603/pathological-levels-of-glucosylceramide-change-the-biophysical-properties-of-artificial-and-cell-membranes
#12
Ana R P Varela, Ana E Ventura, Ana C Carreira, Aleksander Fedorov, Anthony H Futerman, Manuel Prieto, Liana C Silva
Glucosylceramide (GlcCer) plays an active role in the regulation of various cellular events. Moreover, GlcCer is also a key modulator of membrane biophysical properties, which might be linked to the mechanism of its biological action. In order to understand the biophysical implications of GlcCer on membranes of living cells, we first studied the effect of GlcCer on artificial membranes containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM) and cholesterol (Chol). Using an array of biophysical methods, we demonstrate that at lower GlcCer/Chol ratios, GlcCer stabilizes SM/Chol-enriched liquid-ordered domains...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905602/achieving-enhanced-ionic-mobility-in-nanoporous-silica-by-controlled-surface-interactions
#13
Mounesha Nagendrachar Garaga, Luis Aguilera, Negin Yaghini, Aleksandar Matic, Michael Persson, Anna Martinelli
We report a strategy to enhance the ionic mobility in an emerging class of gels, based on robust nanoporous silica micro-particles, by chemical functionalization of the silica surface. Two very different ionic liquids are used to fill the nano-pores of silica at varying pore filling factors, namely one aprotic imidazolium based (1-methyl-3-hexylimidazolium bis(trifluoromethanesulfonyl)imide, C6C1ImTFSI), and one protic ammonium based (diethylmethylammonium methanesulfonate, DEMAOMs) ionic liquid. Both these ionic liquids display higher ionic mobility when confined in functionalized silica as compared to untreated silica nano-pores, an improvement that is more pronounced at low pore filling factors (i...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905601/an-atlas-of-endohedral-sc2s-cluster-fullerenes
#14
Li-Hua Gan, Rui Wu, Jian-Lei Tian, Patrick W Fowler
Structural identification is a difficult task in the study of metallofullerenes, but understanding of the mechanism of formation of these structures is a pre-requisite for new high-yield synthetic methods. Here, systematic density functional theory calculations demonstrate that metal sulfide fullerenes Sc2S@Cn have similar cage geometries from C70 to C84 and form a close-knit family of structures related by Endo-Kroto insertion/extrusion of C2 units and Stone-Wales isomerization transformations. The stabilities predicted for favoured isomers by DFT calculations are in good agreement with available experimental observations, have implications for the formation of metallofullerenes, and will aid structural identification from within the combinatorially vast pool of conceivable isomers...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905600/vuv-photochemistry-of-the-h2oco-complex-in-noble-gas-matrices-formation-of-the-ohco-complex-and-the-hoco-radical
#15
Sergey V Ryazantsev, Luís Duarte, Vladimir I Feldman, Leonid Khriachtchev
Vacuum ultraviolet (VUV, 130-170 nm) photochemistry of the H2OCO complex is studied by matrix-isolation infrared spectroscopy. The H2OCO complexes in Ne, Ar, Kr, and Xe matrices are generated by ultraviolet (UV, 193 and 250 nm) photolysis of formic acid (HCOOH). VUV photolysis of the H2OCO complexes is found to lead to the formation of the OHCO radical-molecule complexes and trans-HOCO radicals. It is shown that the matrix material, local matrix morphology, and possibly the H2OCO complex geometry strongly affect the VUV photolysis pathways...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905599/non-scaling-behavior-of-electroosmotic-flow-in-voltage-gated-nanopores
#16
Cheng Lian, Alejandro Gallegos, Honglai Liu, Jianzhong Wu
Ionic transport through nanopores is of fundamental importance for the design and development of nanofiltration membranes and novel electrochemical devices including supercapacitors, fuel cells and batteries. Recent experiments have shown an unusual variation of electrical conductance with the pore size and the electrolyte parameters that defies conventional scaling relations. Here ionic transport through voltage-gated nanopores was studied by using the classical density functional theory for ion distributions in combination with the Navier-Stokes equation for the electroosmotic flow...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905598/dehydro-oxazole-thiazole-and-imidazole-radicals-insights-into-the-electronic-structure-stability-and-reactivity-aspects
#17
Anamika Mukhopadhyay, Lilit Jacob, Sugumar Venkataramani
DFT (U)B3LYP/cc-pVTZ and (U)M06-2X/cc-pVTZ and multireference CASSCF/cc-pVTZ level of theories have been used to investigate the electronic structure of isomeric dehydrooxazole (1b-d, 3 isomers), dehydrothiazole (2b-d, 3 isomers) and dehydroimidazole (3a-d, 4 isomers) radicals. The ground state electronic structure of each radical isomer has been confirmed by predicting their doublet excited state structure and calculating the adiabatic energy difference. The stability order of the individual isomeric radicals has been estimated through the comparison of absolute energies...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905597/mechanism-for-the-enhanced-oxygen-reduction-reaction-of-la0-6sr0-4co0-2fe0-8o3-%C3%AE-by-strontium-carbonate
#18
Mei Li, Zhongti Sun, Wenqiang Yang, Tao Hong, Zhesheng Zhu, Yanxiang Zhang, Xiaojun Wu, Changrong Xia
Strontium doped lanthanum cobalt ferrite (LSCF) is a widely applied electrocatalyst for the oxygen reduction reaction (ORR) in solid-oxide fuel cells (SOFCs) operated at intermediate temperatures. Sr surface segregation in long-term operation has been reported to have contradicting effects that either degrade or improve the reaction. Thus, it is critical to understand the mechanism of surface Sr compounds on ORR kinetics. This work aims to verify the effect and propose the mechanism by decorating SrCO3 nanoparticles using the infiltration method...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905596/spectral-pointillism-of-enhanced-raman-scattering-for-accessing-structural-and-conformational-information-on-single-protein
#19
Jean-Emmanuel Clément, Aymeric Leray, Alexandre Bouhelier, Eric Finot
In this contribution, we provide new insights on the temporal fluctuations of surface enhanced Raman spectra (SERS) of large single molecules such as proteins. Because they can only fit partly into small active volume, SERS analysis is referred to spectral pointillism where only protein subdomains are shined and the whole protein landscape is built from the dynamics of successive individual spectra. By applying our approach on bovine serum albumin, we show that single protein subdomains are mostly comprised of three distinct amino acids...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905595/self-assembling-reactivity-and-molecular-dynamics-of-fullerenol-nanoparticles
#20
Milan Vraneš, Ivana Borišev, Aleksandar Tot, Stevan Armaković, Sanja Armaković, Danica Jović, Slobodan Gadžurić, Aleksandar Djordjevic
In this work structuring of water and insight into intermolecular interactions between water and fullerenol are studied throughout the process of forming nanoagglomerates at different temperatures applying both experimental and computational approaches. The obtained fullerenol nanoparticles (FNPs) are firstly characterized using dynamic light scattering, atomic force microscopy and transmission electron microscopy. The density, electrical conductivity and dynamic viscosity of aqueous fullerenol solutions are measured in the temperature range of 293...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
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