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.     

N‐Substituted Azacalixphyrins: Synthesis,Properties, and Self‐Assembly

Pre‐ and postintroduction of substituents with respect to the macrocyclization step leads to previously unknown N‐substituted azacalixphyrins. The stepwise synthetic approach has been studied in detail to highlight the key role of the N‐substituents of the precursors and/or intermediates in terms of reactivity. Based on a combined experimental and theoretical investigation, the relationship between the properties of the macrocycles and their degree of substitution is rationalized. Depending on the nature of the N‐substituents, the formation of supramolecular ribbon‐like structures could also be observed, as demonstrated by combined TEM, SEM, AFM, and FTIR experiments.     

Chiral Lithium Amides: Tuning Asymmetric Synthesis on the Basis of Structural Parameters

An overview on the structural arrangements adopted by Chiral Lithium Amides (CLAs), alone or in mixed complexes, is presented. These species are important reagents for asymmetric synthesis and understanding their organization is essential to improve their design and the reaction conditions.     

Modifying polymer flocculants for the removal of inorganic phosphate from water

Due to strong hydrogen bonding interactions, thiourea has been shown to have a high affinity for anions such as inorganic phosphate. The interaction between phosphate and thiourea has been used to develop technologies that can detect and even remove phosphate from water. This research investigates the use of thiourea derivatized polymer flocculants for the sequestering of inorganic phosphate from water. The study presented herein describes the development of a thiourea based monomer that was used to create a bi-functional polymer that flocculates suspended solid material as well as sorbs phosphate, removing both from water. The new polymer removed more than 60% of the phosphate from a simulated wastewater sample. The addition of a thiourea trapping group to the polymer more than doubled the amount of phosphate removed from solution compared to control polymers.     

A convenient route to functionalized 3-amino-N-methylfuro[3,2-b]pyridine-2-carboxamides

The synthesis of novel functionalized 3-amino-N-methylfuro[3,2-b]pyridine-2-carboxamides is described from cyanopyridine intermediates. Based on the difference in halogen reactivity, ethyl [(5-bromo-2-chloropyridin-3-yl)oxy]acetate was functionalized by a palladium-catalyzed reaction, before the cyclization to the desired furo[3,2-b]pyridines.     

Characterization of sprayed and sputtered thin films for lithium ion microbatteries

We have investigated the preparation of thin films of anode and cathode materials for all oxide solid state lithium ion microbatteries. Thin films of LiCoO₂ and Li_4/3Ti_5/3O₄ have been deposited by both spray pyrolysis and RF magnetron sputtering. The structural and electrochemical properties of high temperature-LiCoO₂ thin films have been determined. Spray pyrolysis prepared higher quality LiCoO₂ thin films. Both sprayed and sputtered Li_4/3Ti_5/3O₄ thin films exhibited interesting lithium intercalation capacity. However, it has been demonstrated that RF magnetron sputtering is more efficient than spray pyrolysis for optimizing the interface between Li_4/3Ti_5/3O₄ and the substrate material. Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996     

Improving on the minimum risk equivariant estimator of a location parameter which is constrained to an interval or a half-interval

For location families with densitiesf ₀(x−θ), we study the problem of estimating θ for location invariant lossL(θ,d)=ρ(d−θ), and under a lower-bound constraint of the form θ≥a. We show, that for quite general (f ₀, ρ), the Bayes estimator δ _U with respect to a uniform prior on (a, ∞) is a minimax estimator which dominates the benchmark minimum risk equivariant (MRE) estimator. In extending some previous dominance results due to Katz and Farrell, we make use of Kubokawa'sIERD (Integral Expression of Risk Difference) method, and actually obtain classes of dominating estimators which include, and are characterized in terms of δ _U . Implications are also given and, finally, the above dominance phenomenon is studied and extended to an interval constraint of the form θ∈[a, b]. Research supported by NSERC of Canada.     

A new representation of energy spectra in fully developed turbulence

It is well known that the Kolmogorov 1941 theory is based on global invariance, in the limit of Reynolds number tending to infinity. Experimentally, it is well verified only for very high Reynolds numbers, namelyR 2000 (Monin and Yaglom 1975).We propose a new experimental representation for energy spectra. Using the Kolmogorov scales, a compilation of dimensionless spectra (E= (k)/(v ⁵)^1/4 andK=k(v ³/)^1/4) shows that log(0.154E)/log(R /R*) is a universal function of log(5.42K)/log(R /R*) withR*=75. This new representation is not compatible with neither local nor global scaling invariance. The constant 5.42 takes into account the small scale intermittency. Similar results have been obtained for velocity structure functions of order 2, 3 and 6. In particular the wavenumber constant 5.42 is independent on the order of the moments.