Structure of nanoparticles embedded in micellar polycrystals

We investigate by scattering techniques the structure of water-based soft composite materials comprising a crystal made of Pluronic block-copolymer micelles arranged in a face-centered cubic lattice and a small amount (at most 2% by volume) of silica nanoparticles, of size comparable to that of the micelles. The copolymer is thermosensitive: it is hydrophilic and fully dissolved in water at low temperature (T ~ 0 °C), and self-assembles into micelles at room temperature, where the block-copolymer is amphiphilic. We use contrast matching small-angle neuron scattering experiments to independently probe the structure of the nanoparticles and that of the polymer. We find that the nanoparticles do not perturb the crystalline order. In addition, a structure peak is measured for the silica nanoparticles dispersed in the polycrystalline samples. This implies that the samples are spatially heterogeneous and comprise, without macroscopic phase separation, silica-poor and silica-rich regions. We show that the nanoparticle concentration in the silica-rich regions is about 10-fold the average concentration. These regions are grain boundaries between crystallites, where nanoparticles concentrate, as shown by static light scattering and by light microscopy imaging of the samples. We show that the temperature rate at which the sample is prepared strongly influence the segregation of the nanoparticles in the grain-boundaries.     

Engineering delivery of pantaprazole drug using multi-walled carbon nanotubes: an experimental and theoretical study

Structural Chemistry - Todays, using nano-based drug delivery systems as suitable carriers can help in controlling release of drug to target cells. In current study, multi-walled carbon nanotube...     

Truncation of scales by time relaxation

We study a time relaxation regularization of flow problems proposed and tested extensively by Stolz and Adams. The aim of the relaxation term is to drive the unresolved fluctuations in a computational simulation to zero exponentially fast by an appropriate and often problem dependent choice of its coefficient; this relaxation term is thus intermediate between a tunable numerical stabilization and a continuum modeling term. Our aim herein is to understand how this term, by itself, acts to truncate solution scales and to use this understanding to give insight into parameter selection.     

Isocyanide-based multicomponent reactions: synthesis of 2-(1-(alkylcarbamoyl)-2,2-dicyanoethyl)-N-alkylbenzamide and 1,7-diazaspiro[4,4]nonane-2,4-dione derivatives

A four-component reaction between 2-formylbenzoic acid, malononitrile, isocyanides, and primary alkyl amines has been developed for an efficient preparation of 2-(1-(alkylcarbamoyl)-2,2-dicyanoethyl)-N-alkylbenzamide and 1,7-diazaspiro[4,4]nonane-2,6-dione derivatives under two different conditions. It is shown that simply by changing the reaction solvent from ethanol to dichloromethane and controlling the order of the addition of reagents, two completely different products can be obtained. These multicomponent reactions showed high atom economy.     

Modulation of Fatty Acid Synthase Enzyme Activity and Expression during Hepatitis C Virus Replication

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Highlights? Enzymatic activity of FASN was investigated by ABPP methods during HCV replication ? During HCV replication the activity and expression of FASN increases ? Cellular triglyceride levels rise with increased FASN enzyme activity in Huh7 cells ? Active FASN does not colocalize with HCV replication complexes during HCV replication     

Substituent effects on novel diaminovinylidenes by DFT

Research on Chemical Intermediates - Electronic and steric effects on singlet and triplet symmetric 2,4-diX-vinylidenes with acyclic, cyclic-saturated, and cyclic-unsaturated structures are...     

Zur quantitativen papierchromatographischen Bestimmung der Alkaloide aus Stechapfel (Datura Stramonium)

Zusammenfassung Bekannte papierchromatographische Verfahren zur Trennung der Tropaalkaloide wurden auf ihre Trennleisbung geprüft. Als bestes Fließ-mittelsystem zur Trennung der Alkaloide aus Folia Daturae Stramonii werden wassergesättigtes n-Butanol bzw. Amylalkohol vorgeschlagen. Die Trennung erfolgt auf puff er-imprägnierten Papieren (p_H 7,0 bis 7,6). Die getrennten Alkaloide können nach der Elution aus dem Papier quantitativ photometrisch bestimmt werden. Es wird gezeigt, daß die in Pharmakopöen vorgeschriebenen Methoden zur Bewertung der Droge viel zu hohe Resultate liefern.

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Summary A study was made of the separating efficiency of the known paper chromatography methods of separating the tropaalkaloids. Water-saturatedn-butanol or amyl alcohol were proposed as the best liquid flow system for separating the alkaloids from Folia Daturae Stramonii. The separation occurs on papers impregnated with buffer (pn 7.0 to 7.6). After elution from the paper, the separated alkaloids can be determined quantitatif ely by photometry. It was shown that the methods prescribed in the pharmacopoeias for the assay of drugs yield far too high results.

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Résumé On a étudié le rendement du partage dans les procédés connus de séparation des tropalcaloïdes par chromatographie sur papier. On recommande une solution aqueuse saturée de butanol-n ou d'alcool amylique comme phase mobile la meilleure pour la séparation des alcaloïdes de »Folia Daturae Stramonii«. La séparation s'effectue sur papier imprégné d'un tampon (pH 7,0 à 7,6). On peut doser les alcaloïdes séparés après l'élution du papier, par photométrie. On montre que les méthodes décrites dans les pharmacopées pour l'évaluation de la drogue conduisent à des résultats trop forts.

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Dem Vorstand des Institutes, Frau Prof. Dr. Ing.M. Perpar, sei für die Förderung dieser Arbeit und wertvolle Diskussionen der aufrichtige Dank zum Ausdruck gebracht.     

Molecular dynamics simulation of the diffusion of nanoconfined fluids

A new molecular dynamics simulation technique for simulating fluids in confinement [H. Eslami, F. Mozaffari, J. Moghadasi, F. Müller-Plathe, J. Chem. Phys. 129 (2008) 194702] is employed to simulate the diffusion coefficient of nanoconfined Lennard-Jones fluid. The diffusing fluid is liquid Ar and the confining surfaces are solid Ar fcc (100) surfaces, which are kept frozen during the simulation. In this simulation just the fluid in confinement is simulated at a constant temperature and a constant parallel component of pressure, which is assumed to be equal to the bulk pressure. It is shown that the calculated parallel (to the surfaces) component of the diffusion coefficients depends on the distance between the surfaces (pore size) and shows oscillatory behavior with respect to the intersurface separations. Our results show that on formation of well-organized layers between the surfaces, the parallel diffusion coefficients decrease considerably with respect to the bulk fluid. The effect of pressure on the parallel diffusion coefficients has also been studied. Better organized layers, and hence, lower diffusion coefficients are observed with increasing the pressure.     

A magnetic MoS2-Fe3O4 nanocomposite as an effective adsorbent for dispersive solid-phase microextraction of lead(II) and copper(II) prior to their determination by FAAS

Microchimica Acta - The authors describe the preparation of a nanocomposite (mag-MoS2-Fe3O4) that was prepared from molybdenum disulfide (MoS2) and magnetic Fe3O4 nanoparticles by a hydrothermal...     

Physical stability of oil-in-water emulsions in the presence of gamma irradiated gum tragacanth

Gum tragacanth (GT) exuding from an Iranian Astragalus species was γ-irradiated at 0, 0.75, 1.5, 3, 5, 7, and 10?kGy and used to stabilize a model oil-in-water emulsion system. Stability and physicochemical properties of emulsion samples were investigated with respect to the effect of irradiation treatment on functional properties of gum tragacanth. Particle size distribution, interfacial tension, zeta potential, steady shear, and oscillatory rheological measurements were used to characterize and evaluate the emulsion samples and obtain more information about the possible stability mechanism. Emulsions were prepared by homogenizing 10% w/w sun flower oil with 90% w/w aqueous gum dispersions and stored quiescently at 25°C for 120 days. The results indicated that using 1.5?kGy irradiated GT was more effective in providing optimum values of apparent viscosity, number mean diameter, electrosteric repulsion, and structure strength for getting the maximum emulsion stability. GT significantly reduced the interfacial tension of the oil and water system, but no significant differences were observed among all irradiation treated and non-irradiated samples. This study revealed that GT acts as a bifunctional emulsifier and irradiation treatment has a great positive influence on its ability to reduce droplets’ collision frequency and stabilize the oil-in-water emulsion.