Determination of free and protein-bound glutathione in HepG2 cells using capillary electrophoresis with laser-induced fluorescence detection

A rapid method using capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was developed to determine free and protein-bound glutathione (GSH) in human HepG2 hepatocarcinoma cells. The samples were derivatized with 5-iodoacetamidofluorescein (5-IAF), and analyzed at 22 kV using sodium phosphate buffer (10mM, pH 11.4) and an uncoated 58 cm x 75 microm I.D. fused silica capillary. The analysis time was less than 10 min and N-acetylcysteine was used as internal standard. The derivatization conditions, such as reaction time, 5-IAF concentration, running buffer and cartridge temperature were optimized. Argon gas was used in the study to prevent the oxidization of GSH during sample preparation. The optimized method required only 30-40 nl sample per analysis and was fast and sensitive. The method was applied to the analyses of HepG2 cells treated with the small metal chelating agent, pyrrolidine dithiocarbamate (PDTC). The results demonstrate that the amount of protein-bound GSH, which reflects the amount of protein S-glutathionylation, increased in a time-dependent manner upon cell treatment with PDTC, reaching a maximum of over 50% increase 2h post-PDTC.     

Silylated Melamine and Cyanuric Acid as Precursors for Imprinted and Hybrid Silica Materials with Molecular Recognition Properties

Imprinted materials : Monosilylated derivatives of melamine and cyanuric acid are used in the preparation of hybrid silica. The assembly of the melamine and cyanuric acid moieties through molecular recognition properties is the key factor in building a bridged silsesquioxane and an imprinted hybrid silica (see picture).

     

Evaluation of solid-phase microextraction as an alternative to the official method for the analysis of organic micro-pollutants in drinking water

The objective this study was to compare the official EU liquid-liquid extraction (LLE) method with solid-phase microextraction (SPME) for the analysis of compounds migrating from cross-linked polyethylene into water. A medium polarity polydimethylsiloxane/divinylbenzene (PDMS/DVB) 65 microm fibre proved most efficient for the SPME extraction of nine test compounds and the optimum extraction conditions were an immersion time of 30 min with heating to 60 degrees C. The repeatability of the SPME method was variable: RSD values ranged from approximately 4-18% depending on the individual compound, though correlation coefficients were greater than 0.999 in the concentration range 0.5-1000 microg/l. It would also seem that there is some competition amongst different compounds for sites on the fibre and this is a potential drawback of SPME when applied to unknown samples. However, when applied to water samples in contact with polyethylene, SPME proved to be immensely more sensitive and to have a greater extraction range than LLE. These factors coupled with the rapidity and ease of use of SPME mean that it could be developed for use as an alternative to the existing official method or as an alert system in the routine analysis of materials used to transport domestic water.     

Homoleptic 2-mercapto benzothiazolate uranium and lanthanide complexes

Treatment of [Ln(BH 4) 3(THF) 3] (Ln = Ce, Nd) with 3 and 4 mol equiv of KSBT in tetrahydrofuran (THF) led to the formation of [Ln(SBT) 3(THF)] and [K(THF)Ln(SBT) 4], respectively. The uranium(IV) compound [U(SBT) 4(THF) 2] was obtained from U(BH 4) 4 and was reversibly reduced by sodium amalgam into the corresponding anionic uranium(III) complex. The crystal structures of [Ln(SBT) 3(THF) 2] (Ln = Ce, Nd), [K(15-crown-5) 2][Nd(SBT) 4], [U(SBT) 4(THF)], and [K(15-crown-5) 2][U(SBT) 4(py)] show the bidentate coordination mode and the thionate character of the SBT ligand.     

Microhydration effects on the electronic spectra of protonated polycyclic aromatic hydrocarbons: [naphthalene-(H2O)(n = 1,2)]H+

Vibrational and electronic spectra of protonated naphthalene (NaphH(+)) microsolvated by one and two water molecules were obtained by photofragmentation spectroscopy. The IR spectrum of the monohydrated species is consistent with a structure with the proton located on the aromatic molecule, NaphH(+)-H(2)O. Similar to isolated NaphH(+), the first electronic transition of NaphH(+)-H(2)O (S(1)) occurs in the visible range near 500 nm. The doubly hydrated species lacks any absorption in the visible range (420-600 nm) but absorbs in the UV range, similar to neutral Naph. This observation is consistent with a structure, in which the proton is located on the water moiety, Naph-(H(2)O)(2)H(+). Ab initio calculations for [Naph-(H(2)O)(n)]H(+) confirm that the excess proton transfers from Naph to the solvent cluster upon attachment of the second water molecule.     

Synthesis and cytotoxic activity of 11-nitro and 11-amino derivatives of acronycine and 6-demethoxyacronycine

Condensation of 2-chloro-3-nitrobenzoic acid with either 5-amino-7-methoxy-2,2-dimethyl-2H-chromene or 5-amino-2,2-dimethyl-2H-chromene afforded diphenylamines 14 and 15. Trifluoroacetic anhydride mediated cyclization gave the corresponding acridones 16 and 17, which were subsequently N-methylated and reduced to 11-aminoacronycine and 11-amino-6-demethoxyacronycine. These two amino compounds, which gave stable water soluble salts, were 2- to 3-fold more potent than acronycine or 6-demethoxyacronycine in inhibiting L1210 cell proliferation.     

Six-fold oxygen-coordinated triplet (S = 1) palladium(II) moieties templated by tris(bipyridine)ruthenium(II) ions

Tris(bipyridine)ruthenium(II) is used as a templating agent to insert palladium(II) into three-dimensional oxalate-based networks. The templated-assembly of [Ru(bpy)(3)][Pd(2)(ox)(3)] (Pd(2)) and [Ru(bpy)(3)][PdMn(ox)(3)] (PdMn) is described. The latter compound is structurally characterized by powder X-ray diffraction and X-ray absorption spectroscopy. These techniques reveal an unusual 6-fold oxygen environment around the Pd(II) atoms with two short (2.02 Angstrom) and four long (2.17 Angstrom) Pd-O distances. As stated by magnetometry, this environment is associated with a triplet ground state (S = 1) of the palladium(II) ion: when the temperature is decreased, the chiMT product shows a monotonous decrease from 5.54 cm(3) K mol(-1) at 300 K, a value which is slightly lower than the one expected for independent paramagnetic Pd(II) (S = 1, g = 2) and Mn(II) (S = 5/2, g = 2) ions. This thermal variation is due to antiferromagnetic exchange interactions between the two spin bearers. Nevertheless, no long-range magnetic order is detected down to 2 K. These results are confirmed by an analysis of the [MII(C(2)O(4))(3)](4-) (M = Ni, Pd, Pt) complex and of a [Pd(II){mu-(C(2)O(4))Mn(II)(OH(2))(4)}(3)](2+) tetranuclear model using density functional theory.     

Electron pair localization function: a practical tool to visualize electron localization in molecules from quantum Monte Carlo data

In this work we introduce an electron localization function describing the pairing of electrons in a molecular system. This function, called "electron pair localization function," is constructed to be particularly simple to evaluate within a quantum Monte Carlo framework. Two major advantages of this function are the following: (i) the simplicity and generality of its definition; and (ii) the possibility of calculating it with quantum Monte Carlo at various levels of accuracy (Hartree-Fock, multiconfigurational wave functions, valence bond, density functional theory, variational Monte Carlo with explicitly correlated trial wave functions, fixed-node diffusion Monte Carlo, etc). A number of applications of the electron pair localization function to simple atomic and molecular systems are presented and systematic comparisons with the more standard electron localization function of Becke and Edgecombe are done. Results illustrate that the electron pair localization function is a simple and practical tool for visualizing electronic localization in molecular systems.     

Der Stein-Chensche Ansatz zur Poisson-Approximation und zum Beweis des Zentralen Grenzwertsatzes

Zusammenfassung.   Befa?t man sich in der Didaktik mit stochastischen Fragestellungen, so ben?tigt man bei Anwendungen früher oder sp?ter den Zentralen Grenzwertsatz der Wahrscheinlichkeitstheorie. Ein Beweis seiner allgemeinen Fassung wird dabei nirgendwo ausgeführt, denn “dieser Satz ist schwer zu beweisen” (Scheid [11], Seite 103). Siehe dazu auch Krickeberg-Ziezold [8], Seite 106: “Der Beweis dieses Satzes bedarf allerdings zu vieler analytischer Hilfsmittel, als da? er im Rahmen dieses Buches pr?sentiert werden k?nnte“. Mit Hilfe der Steinschen Methode leiten wir auf elementare Art und Weise eine Fehlerschranke her, die die klassische Form des Zentralen Grenzwertsatzes sowie einen Spezialfall des Satzes von Berry-Esséen über die dort vorliegende Konvergenzordnung impliziert. Dabei wird beim Beweis neben einfachen Umformungen nur der Satz von Fubini über die Vertauschbarkeit der Integrationsreihenfolge bei Mehrfachintegralen ben?tigt. Im Zusammenhang mit der Poisson-Approximation der Binomial-Verteilung wurde die Steinsche Methode zuerst von Chen [5] angewandt; die lange gesuchte “optimale” Fehlerschranke leiteten schlie?lich Barbour und Hall [2] her. Verwiesen sei in diesem Zusammenhang insbesondere auf das Buch von Barbour et al. [3]. Einen Gesamtüberblick über beide Themenkreise, die vielf?ltigen weiteren Anwendungen der Steinschen Methode und ausführliche Literaturhinweise findet man bei Barbour [1]. Hier wollen wir über den Begriff der Strukturfunktionen beide Ans?tze soweit wie m?glich vereinheitlichen und die faszinierende Idee sowie die elementaren Beweise einem breiteren Publikum vorstellen. Eingegangen 06.12.1996 / Angenommen 06.03.1998