Simultaneous analysis of oxidized and reduced glutathione in cell extracts by capillary zone electrophoresis

Glutathione (GSH) and glutathione disulfide (GSSG) levels in cells constitute a thiol redox system. They can be used as an indicator of oxidative stress of the cell. In this study, a capillary zone electrophoresis (CZE) method is described that enables quantitation of GSH and GSSG from cellular extracts. The CZE buffer used was 20 mM ammonium acetate containing 5% (v/v) acetic acid at pH 3.1 in conjunction with a polybrene coated capillary operated in reverse polarity mode. Effects of different acids used to prepare cell samples were investigated on CZE performance. The acids include meta phosphoric acid (MPA), trichloroacetic acid (TCA), phosphoric acid (PA) and sulfosalicylic acid (SSA) and are used to stabilize GSH and GSSG before performing CZE analysis. The method features a limit of detection of 4 microM and a limit of quantitation of 12 microM for both GSSG and GSH and recoveries of 94% for GSH and 100% for GSSG. Quantitative analysis of GSSG and GSH in HaCaT cell extracts (5% SSA, w/v) was performed with this method and changes in the ratio of GSH to GSSG in N-ethylmaleimide treated cell sample was observed by comparing with control cell samples.     

(1-Adamantanethio)pyridines and tetrahydropyridines from the reaction of 1-adamantanethiol with pyridine I-oxide in acetic anhydride

The reaction of pyridine 1-oxide with 1-adamantanethiol in acetic anhydride produced a mixture of 2- and 3-(1-adamantanethio)pyridines, 1-aeetyl-2-(1-adamantanethio)-3-hydroxy-4-acetoxy-1,2,3,4-telrahydropyridine and the corresponding 3-acetoxyderivative. Pure substances were separated by means of column chromatography on alumina. The tetrahydropyridines were identified by means of their proton magnetic and mass spectra. 4-(1-Adamantanethio)pyridine was synthesized from 4-chloropyridinc and 1-adamantanethiol. The three isomeric (1-adamantanethio)-pyridines were, each, cleaved by concentrated hydrochloric acid to give 1-chloroadamantane and the corresponding pyridinethiol.     

A class of means and related inequalities

The aim of this paper is two-fold: First we describe a certain class of strictly positive, continuous functions u:I defined on certain intervals I]0,+[, and demonstrate that each function u of this class permits the definition of an associated mean M_u (a₁,...,a_n) for any finite number a₁,...,a_n of numbers in I. The arithmetic and the geometric mean are special cases of these u-means M_u. -Thereafter, we improve the classical inequality between the geometric and the arithmetic mean and derive from it a corresponding inequality between certain u-means and the arithmetic mean.     

X-ray structure and variable temperature NMR spectra of [meso-triarylcorrolato]copper(III)

The diamagnetic square planar d(8) complexes [meso-arylcorrolato]copper(III) become paramagnetic upon warming, indicative of the equilibrium between the [corrolato]copper(III) and the [corrolato](+)* copper(II) forms of the complex. [meso-Triphenylcorrolato]copper(III) was structurally characterized and found to be saddled.     

Nanostructure investigations with the analytical transmission electron microscope

Concerning the conventional TEM-imaging as well as the analytical procedures the capabilities are pointed out: electron diffraction, energy dispersive X-ray spectroscopy (EDXS) and electron energy loss spectroscopy (EELS). The possibilities of investigation of both nanocrystalline materials and multilayers are discussed, accompanied by examples of current investigations: At alloys, produced by intense milling, at single nanocrystals the imaging by diffraction contrast was successful, the analysis has failed because of the sample thickness. By means of energy spectroscopic imaging multilayers from Fe-SiB/NbCu and Fe/Cr as well as Al₂O₃/TiN have been characterized. Received: 15 July 1997 / Revised: 16 February 1998 / Accepted: 21 February 1998     

Acidité dans le nitrométhane: III. Détermination électrochimique de la basicité du nitrométhane — Corrélation Dn/Eo(Hs+/H2/

The use of the complex acid HAlCl₄ (HCl+AlCl₃) permits the detemrination of the standard potential of the hydrogen electrode in nitromethane. The result (E₀(H_s⁺/H₂)=0.5 V vs. Fc/Fc⁺, Fc=ferrocene) shows that nitromethane is very weakly basic. This measurement is confirmed by showing that the standard potential of the hydrogen electrode in various solvents is linked to Gutmann's donor numbers of these solvents. The E₀(H_s⁺/H₂) value obtained in nitromethane belongs to the correlation line.     

Influence of the three-dimensional heterogeneous roughness on electrokinetic transport in microchannels

Surface roughness has been considered as a passive means of enhancing species mixing in electroosmotic flow through microfluidic systems. It is highly desirable to understand the synergetic effect of three-dimensional (3D) roughness and surface heterogeneity on the electrokinetic flow through microchannels. In this study, we developed a three-dimensional finite-volume-based numerical model to simulate electroosmotic transport in a slit microchannel (formed between two parallel plates) with numerous heterogeneous prismatic roughness elements arranged symmetrically and asymmetrically on the microchannel walls. We consider that all 3D prismatic rough elements have the same surface charge or zeta potential, the substrate (the microchannel wall) surface has a different zeta potential. The results showed that the rough channel's geometry and the electroosmotic mobility ratio of the roughness elements' surface to that of the substrate, epsilon(mu), have a dramatic influence on the induced-pressure field, the electroosmotic flow patterns, and the electroosmotic flow rate in the heterogeneous rough microchannels. The associated sample-species transport presents a tidal-wave-like concentration field at the intersection between four neighboring rough elements under low epsilon(mu) values and has a concentration field similar to that of the smooth channels under high epsilon(mu) values.     

Über die Konstitution eines Nebenalkaloides aus Adhatoda vasica Nees

Zusammenfassung Das in der vorangehenden Mitt. vonE. Späth undF. Gandini-Kesztler beschriebene Nebenalkaloid wird auf synthetischem Wege mit dem 6-Hydroxy-peganin identifiziert. Die phenolische OH-Gruppe steht also, bezogen auf Formel III, nicht an der Stelle, welche dem CH₃O des Harmins entspricht.     

Selective Si--C bond cleavage as synthetic entry to a functionalized lithiosilane

Treatment of the phenyl-substituted silane 4 with lithium metal afforded the functionalized lithiosilane rac-2 by selective cleavage of one Si-C bond between silicon and a phenyl group. The resulting lithiosilane rac-2 crystallizes as the dimer (2.THF)2, which represents the first example of a dimeric organyl-substituted lithiosilane in the presence of THF.     

A new class of C1-symmetric monosulfoximine ligands for enantioselective hetero Diels-Alder reactions

Quinoline-based C1-symmetric sulfoximines have been used as chiral ligands in copper-catalyzed asymmetric hetero Diels-Alder reactions leading to cycloadducts with up to 96% ee.