NMR and X-ray diffraction studies of the influence of adsorbed molecule nature on phase transitions in a ZSM-5 silicalite

Pulsed NMR and X-ray diffraction analysis are employed to study the influence of adsorbed toluene, p-xylene, acetone, and di(ethylene glycol) (DEG) molecules on phase transitions in a ZSM-5 silicalite. In the region of phase transitions, times T₁ and T₂ of longitudinal and transverse magnetic relaxation of apolar molecules adsorbed in silicalite micropores increase and decrease in a jumpwise manner, respectively, with a rise in the total content of the liquid. Such changes in T₁ and T₂ occur for hexane, decane, toluene, and p-xylene molecules. Qualitatively different concentration dependences of T₁ and T₂ are observed for polar acetone and DEG molecules, because these liquids do not cause a earrangement in the crystal lattice of silicalite; this is confirmed by the X-ray diffraction data.Translated from Kolloidnyi Zhurnal, Vol. 66, No. 6, 2004, pp. 802–806.Original Russian Text Copyright © 2004 by Pimenov, Skirda, Maksimenko, Morozov, Opanasyuk.     

Determination of phenolic components in ethanolic extracts from wood of Maackia amurensis

The phenolic components in an ethanolic extract from the wood of Amur maackia were determined quantitatively by the HPLC method in the isocratic regime using a column with a C₁₉ reversed-phase sorbent and β-naphthol acetate as internal standard. Before injection into the chromatographic column, the extract was purified on a column of Florisil that had been treated with 30% acetic acid. The relative error in the determination of each component at a confidence level of 0.95 does not exceed 7%.     

Quantitative analysis of 3-indoleacetic acid and serotonin by in situ fluorescence on thin-layer chromatograms

Summary The characterization and quantitation of indoles by thin-layer chromatography followed by fluorometric scanning of the chromatographed species on the thin-layer provides a rapid and sensitive method of analysis at theg level and lower. Considerable increases in fluorescence intensity may be achieved if the plate is sprayed with a polar compound such as dimethylsulfoxide prior to measurement. The method may be used to quantitatively determine directly 50 ng samples of serotonin and indoleacetic acid and should be equally sensitive for other indolic compounds. The analysis of biological extracts for low levels of indoles should be a particular application for the method.

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Zusammenfassung Die Charakterisierung und Bestimmung von Indolen durch Dünnschicht-chromatographie und nachfolgende Fluoreszenzmessung der chromatographierten Substanzen auf der Dünnschichte erfordert eine rasche und empfindliche Analysenmethode für die Größenordnung von Mikrogramm und darunter. Eine erhebliche Verstärkung der Fluoreszenz läßt sich durch Sprühen mit einer polaren Verbindung wie z. B. Dimethylsulfoxid erreichen. Diese Bestimmungsmethode eignet sich für die direkte Bestimmung von 50 ng Serotonin und Indolessigsäure und dürfte auch für andere Indolderivate gleich empfindlich sein. Insbesondere Extrakte biologischen Materials dürften sich zur Analyse anbieten.

     

Generalization of Dewar's half-electron method for calculating energies of open-shell electronic states

Dewar's “half-electron” model for calculating electronic energies of certain open-shell doublet and triplet states is extended so as to be applicable to the lowest-energy open-shell state of any given symmetry and multiplicity.     

Wirkung von antithyreoidalen Substanzen auf Kupfer-Enzyme bei Pilzen und Coeruloplasmin in vitro

Zusammenfassung Antithyreoidale Substanzen, die in ihrer Struktur die Thiourylengruppe besitzen, inhibieren einerseits die Aktivität der Tyrosinoxydase von Pilzen in vitro, und andererseits zerstören sie den Proteinkomplex des Blutes, Coeruloplasmin. Die Reaktion findet bei einem Überschuß des Stoffes statt und ist irreversibel. Nach den Ergebnissen läßt sich nicht feststellen, daß der Angriff in beiden Fällen identisch ist. Die Tyrosinoxydase der Pilze wird durch alle Substanzen, die eine antithyreoidische Aktivität aufweisen, inhibiert; Coeruloplasmin wird durch nichtsubstituierte Moleküle zerstört.

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Effect of strumigens on copper enzymes of fungi and coeruloplasmin in vitro

Strumigens containing the thiurylene group inhibit in vitro the activity of thyrosinoxydase in fungi and destroy the Cu-protein complex of blood, coeruloplasmin. The reaction takes place only when there is a surplus of strumigens and is irreversible. According to results it is not possible to state that the interference with both enzyme systems is identical. Thyrosinoxydase of fungi was inhibited by substances identical with their goitrogen-activity; coeruloplasmin was destroyed by non-substituted molecules.

     

New prodrugs derived from 6-aminodopamine and 4-aminophenol as candidates for melanocyte-directed enzyme prodrug therapy (MDEPT)

Two novel tyrosinase mediated drug delivery pathways have been investigated for the selective delivery of cytotoxic units to melanocytes from urea and thiourea prodrugs. The synthesis of these prodrugs is reported, as well as oximetry data that illustrate that the targets are substrates for tyrosinase. The stability of each of the prodrugs in (i) phosphate buffer and (ii) bovine serum is discussed, and the urea prodrugs are identified as lead candidates for further studies. Finally, HPLC studies and preliminary cytotoxicity studies in a melanotic and an amelanotic cell line, that illustrate the feasibility of the approach, are presented.     

Magnetic properties of nanosized hexaferrite powders

Hexagonal ultradispersed ferrites were obtained in a high energy planetary mill by mechanochemical treatment. Their structural characteristics — average size and internal stress — were studied. Fundamental magnetic characteristics — saturation magnetization and effective fields of crystal anisotropy — were examined in pulse magnetic fields with the law of approach to saturation, as well as by ferromagnetic resonance technique in the 26–53 GHz frequency range. It was demonstrated that size reduction of powders to a few tens of nanometers influenced significantly the effective anisotropy field. A model accounting for anisotropy contribution from the disturbed subsurface layer and magnetoelastic interactions was suggested. Mechanical activation was shown to be an alternative to chemical substitution for magnetic anisotropy control.     

Gasanalyse mit Hilfe eines kleinen Massenspektrometers

Zusammenfassung Es wird eine automatisierte Apparatur zur schnellen, massenspektrometrischen Bestimmung von Sauerstoff und Stickstoff in Stahl beschrieben. Die Stahlprobe wird unter Argon im Gleichstrombogen geschmolzen und die extrahierten Gase Kohlenmonoxid und Stickstoff werden massenspektrometrisch bestimmt. Die relative Standardabweichung beträgt ±3–5% für Sauerstoff und ±3–8% für Stickstoff. Die Nachweisgrenzen liegen bei 10 pp10⁶ O₂ und 3 pp10⁶ N₂. Der Zeitbedarf für eine Analyse beträgt 85 s.Herrn H. Siffrin danke ich für die sorgfältige Durchführung der zahlreichen Versuche.     

Differentiation effect of solvents on the keto-enol equilibrium of heterocyclic β-dicarbonyl compounds

The differentiation effect of a solvent on the equilibrium of five- and six-membered heterocyclic β-keto esters and β-diketones containing =O, =S, =SO, =NR, =NRHC1, and -S-C(R)₂-S-fragments and, for comparison, on the equilibrium of aliphatic and carbocyclic β-keto esters and β-diketones was studied. The differentiating effect of a solvent is explained by different kinds of solvation of the heteroatomic fragments in the ketone and enol forms of heterocyclic β-dicarbonyl compounds.     

TiO2 sol-gel derived amperometric biosensor for H2O2 on the electropolymerized phenazine methosulfate modified electrode

A novel hydrogen peroxide biosensor was developed based on the immobilization of horseradish peroxidase (HRP) in a TiO(2) sol-gel matrix on an electropolymerized phenazine methosulfate (PMS) modified electrode surface. Such membranes are of interest due to their high surface area, biological compatibility, and ease of fabrication. HRP entrapped in the TiO(2) matix was stable and retained its activity to a large extent. Cyclic voltammetry and amperometric measurements were employed to demonstrate the feasibility of electron transfer between immobilized HRP and the glassy carbon electrode via electropolymerized PMS. The influence of various experimental parameters such as operating potential, pH, temperature, and stability was investigated for optimum analytical performance. The biosensor provided a wide linear calibration range from 4.0x10(-6) M to 1.0x10(-3) M, with a detection limit of 8.0x10(-7) M at a signal-to-noise ratio of 3. The sensor retained 80% of its original activity after two months of operation.