Development of a fluorescence-based microtiter plate method for the measurement of glutathione in yeast

The present work was aimed to the development of a fluorescence assay using the universal 96-well microplate format, for the measurement of reduced glutathione (GSH) in yeast cells. The method relies upon the reaction between GSH and a highly selective fluorogenic probe, i.e. naphthalene-2,3-dicarboxaldehyde (NDA). The optimization of the method included the extraction step of GSH from cultured yeast cells in a cold perchloric acid solution, derivatization conditions (10-min reaction at pH 8.6 and at 20 ± 2 °C in darkness) and stability studies of the resulting fluorescent adduct. Full selectivity was observed versus other endogenous thiols (except for γ-glutamylcysteine), glutathione disulfide (GSSG) and enzymatic reducing reagents of GSSG. Linearity was verified in the range 0.3-6.5 μM (R² > 0.98) and limits of quantification and detection were 0.3 and 0.05 μM, respectively. Relative standard deviation corresponding to repeatability (n = 3) and inter-day precision (n = 5) were 2.8 and 6.1%, respectively. Mean GSH recovery from cell extracts was 95%. The method appeared highly correlated (R² = 0.96) with a previously reported HPLC method.The method was then applied to the monitoring of GSH in the yeast strain Kluyveromyces lactis during its growth period and in the presence of an inhibitor of GSH biosynthesis. The method presents the main advantage of a high throughput for the measurement of biological samples. The extent of the method to the study of the redox couple GSSG/GSH by including an enzymatic reduction step and the enhancement of the fluorescence signal using cyclodextrins were discussed.     

Quantum Size Effect and very localized random laser in ZnO@mesoporous silica nanocomposite following a two-photon absorption process

ZnO@mesoporous silica nanocomposite was prepared by the impregnation of a CMI-1 material in a Zn(NO₃)₂ solution followed by calcination under O₂. Intensive characterization was carried out by N₂ adsorption–desorption measurements, scanning and transmission electron microscopy. The optical properties of the ZnO@mesoporous silica nanocomposite were studied by photoluminescence spectroscopy. Quantum Size Effect was firstly demonstrated by subjecting the sample to a 254 nm excitation light, and was further confirmed by using a 680 nm excitation laser beam, which implies a two-photon absorption process. By focusing the 680 nm laser beam on different places in the sample, a very localized random laser effect, also induced by a two-photon absorption process, was detected.     

2-Pyridinealdoxime, a new ligand for a Pd-precatalyst: Application in solid-phase-assisted Suzuki–Miyaura reaction

Summary The preparation of a new palladium(II) complex with a 2-pyridinealdoxime ligand and its use as a Pd(0) precatalyst in the cross-coupling Suzuki–Miyaura reaction is described. Several concepts for the immobilization of this catalytic system are presented and compared in order to develop an efficient catalytic tool for high-throughput synthesis     

Stability problem for number-theoretically multiplicative functions

We deal with the stability question for multiplicative mappings in the sense of number theory. It turns out that the conditional stability assumption:

   for relatively prime 

implies that lies near to some number-theoretically multiplicative function. The domain of can be general enough to admit, in special cases, the reduction of our result to the well known J. A. Baker - J. Lawrence - F. Zorzitto superstability theorem.

     

The p–T phase diagram for ferroelectric bis-thiourea pyridinium nitrate

The effect of temperature and pressure on physical properties of the ferroelectric bis-thiourea pyridinium nitrate inclusion compound has been studied by dielectric spectroscopy and nuclear magnetic resonance (NMR). At ambient pressure the ferroparaelectric phase transition observed at T₂ = 216 K is continuous in contrast to the nonferroelectric phase transition observed at T₁ = 273 K. Under small pressures, the temperatures of the phase transitions T₁ and T₂ increase with increasing pressure. Starting from about 250 MPa, T₁ temperature decreases with increasing pressure, while T₂ temperature increases with increasing pressure. At 450 MPa and 245 K a triple point is observed. Bis-thiourea pyridinium nitrate undergoes a continuous phase transition from the ferroelectric to paraelectric phase under 450 MPa, while above this pressure the phase transition from the ferroelectric to paraelectric phase is discontinuous. The change in the phase transition character is related to the crystallographic change in the group–subgroup relation between the ferro- and paraelectric phases taking place with increasing pressure.     

Treatment of advanced divertor configurations in the flux-coordinate independent turbulence code GRILLIX

Advanced divertor configurations modify the magnetic geometry of the divertor to achieve a combination of strong magnetic flux expansion, increased connection length and higher divertor volume—to improve detachment stability, neutral/impurity confinement and heat-channel broadening. In this paper, we discuss the modification of the flux-coordinate independent (FCI) turbulence code GRILLIX to treat generalized magnetic geometry, to allow for the investigation of the effect of magnetic geometry on turbulent structures in the edge and scrape-off layer (SOL). The development of grids and parallel operators from numerically defined magnetic equilibria is discussed, as is the application of boundary conditions via penalization, with the finite-width method generalized to treat complex non-conformal boundaries. Initial testing of hyperbolic (advection) and parabolic (diffusion) test cases are presented for the Snowflake scenario.     

Fe- and Cu-oxides supported on γ-Al2O3 as catalysts for the selective catalytic reduction of NO with ethanol. Part I: catalyst preparation,characterization, and activity

Fe- and Cu-oxides supported on γ-alumina (γ-Al₂O₃; metal loading of 3 mass %) were investigated as alternative catalysts to the conventional Ag-based system in the selective catalytic reduction of NO with ethanol (EtOH-SCR). The catalysts were characterized by elemental analysis, N₂ sorption, X-ray diffraction, temperature-prgrammed desorption of NH₃, temperature-programmed reduction with H2, diffuse reflectance UV-VIS (DR-UV-VIS) spectroscopy, and compared with 3 mass % Ag/γ-Al₂O₃ as a reference catalyst. Catalytic experiments were carried out between 423 K and 773 K in the steady state and by temperature-programmed surface reaction (TPSR) experiments. For all catalysts, the highest NO conversion (900 ppm (ppm = parts of the mixture component per million parts of all mixture components) NO, 900 ppm EtOH, 0.5 vol. % H₂O, 4 vol. % O₂ in He) was found at 573 K. While 84 % of NO were converted over the Ag-based catalysts, only 20–60 % NO conversion was observed for the Fe- and Cu-containing catalysts. Total oxidation of ethanol as an unwanted side reaction occurs over 3 mass % Cu on γ-Al₂O₃ already at 573 K, whereas the highest activity of 3 mass % Fe on γ-Al₂O₃ for this conversion was reached at 743 K. For lower temperatures, partial oxidation of ethanol leads to organic by-products which can act as active intermediates in EtOH-SCR. TPSR experiments show that ethanol reacts over both the Fe- and the Cu-based catalysts to organic by-products, such as ethene or acetaldehyde, which affect the EtOH-SCR reaction.     

Minimal Shape-Preserving Projections Onto Π n : Generalizations and Extensions

The goal of this paper is to further the investigation begun in Chalmers and Prophet, Numer. Funct. Anal. Optimiz. 1997; 18:507–520. With the benefit of nearly 10 years of work, we begin by indicating how several proofs from Chalmers and Prophet, Numer. Funct. Anal. Optimiz. 1997; 18:507–520, can be substantially improved. We show that the problem of preserving k-convexity onto Π _n is one part of a larger shape-preserving problem (multiconvex preservation) relative to Π _n , and we completely solve this expanded problem. And finally, we demonstrate that multiconvex preserving projections constructed in this paper are in fact of minimal operator norm in a large class of Banach spaces.     

Application of splines for determining the velocity characteristic of a medium from a vertical seismic survey

A method for solving the inverse kinematic problem of determining the velocity characteristic of a medium from a vertical seismic survey, is proposed. It is based on the combined use of the eikonal equation and spline methods of approximation for multivariable functions. The problem is solved by assuming a horizontally stratified medium; no assumptions about the number of layers and their thickness are made. First, using the data of the first arrival times of the seismic signal from several shotpoints, which are registered by detectors located in the vertical borehole, a spline approximating the function of first arrival time of the signal from source points to any point in the Earth subsurface is constructed. Then with the help of the eikonal equation, the characteristic of the medium around the borehole is determined. Numerical experiments on the model and the real data show high efficiency of the proposed method.