In vitro nitrosation of insulin A- and B-chains

The physiological roles of insulin and nitric oxide (NO) have been recently recognized by several studies. A diversity of chemical modifications of insulin is reported both in vivo and in vitro. S-nitrosation, the covalent linkage of NO to cysteine free thiol is recognized as an important post-translational regulation in many proteins. Here we report the in vitro synthesis of an S-nitrosothiol of bovine insulin A- and B-chains. These compounds were characterized by their HPLC chromatographic behavior, monitored by UV visible spectroscopy and electron spray ionization mass spectrometry. The experimental results indicate that each A- and B-chain were S- nitrosated with only one NO group. Stability and solubility of these synthesized derivatives is described for physiological purposes. In this work, nitroso A- and B-chains of insulin were synthesized in vitro in order to better understand the possible interactions between insulin and NO that may be involved in the etiology of insulin resistance.     

Correction to critical pairs of matrices for the degree of the minimal polynomial of the kronecker sum

We present a correction to the main theorem in the article "Critical Pairs of Matrices for the Degree of the Minimal Polynomial of the Kronecker Sum", Volume 42 (1997) pages 73-88.     

Characterization and kinetic study of sunflower oil and biodiesel

In this study, the physico-chemistry characterization and kinetic study of the thermal decomposition of sunflower oil and its biodiesel were carried out. Sunflower biodiesel was synthesized by the methanol route and basic homogeneous catalysis. The physicochemical characterization of the sunflower oil and biodiesel were performed according to standards set out in the ANP resolution, and both are in accordance to the specifications. The chromatographic analysis was obtained by GC-FID. The yield of conversion of 97.4 wt% of sunflower oil in methyl esters confirms the efficiency of the conversion of the fatty acids into esters. The thermal analysis was performed on a thermobalance, using heating rates of 5, 10, and 20 °C min⁻¹. In these three rates, we observed a single well-defined step of mass loss that describes the volatilization and decomposition of the sunflower oil and the biodiesel. The kinetic study was performed using equations of approximation and integration methods such as Coats–Redfern, Van Krevelen, and Horowitz–Metzger. The kinetic parameters reaction order (n) and apparent activation energy (E _a), obtained by applying these method were correlated.     

Bosonization approach for bilayer quantum Hall systems at nu(T)=1

We develop a nonperturbative bosonization approach for bilayer quantum Hall systems at nu(T)=1, which allows us to systematically study the existence of an exciton condensate in these systems. An effective boson model is derived and the excitation spectrum is calculated in both the Bogoliubov and the Popov approximations. In the latter case, we show that the ground state of the system is an exciton condensate only when the distance between the layers is very small compared to the magnetic length, indicating that the system possibly undergoes another phase transition before the incompressible-compressible one. The effect of a finite electron interlayer tunneling is included and a quantitative phase diagram is proposed.     

Behaviour of Low Molecular Weight Compounds,Iron and Copper of Wine Spirit Aged with Chestnut Staves under Different Levels of Micro-Oxygenation

Alternative technologies for a more sustainable wine spirits’ ageing have been studied but a lack of knowledge on the effect of oxygenation level remains. This work examined the behaviour of low molecular weight compounds, iron and copper of a wine spirit aged in 50 L demijohns with chestnut wood staves combined with three levels of micro-oxygenation or nitrogen. Compounds and mineral elements were quantified by HPLC and FAAS, respectively, in samples collected at 8, 21, 60, 180, 270 and 365 days of ageing. Results showed that most of the compounds underwent significant changes in their content over time and behave differently depending on the wine spirit’s oxygenation level: higher contents of gallic acid, syringic acid and vanillin were associated with lower micro-oxygenation level while higher contents of ellagic acid, syringaldehyde, coniferaldehyde and sinapaldehyde resulted from higher one; lowest contents of these compounds were found in the nitrogen modality. Weak correlation between copper and the studied compounds was evidenced whereas closer relationship between iron, vanillin, gallic, syringic and ellagic acids at end of ageing was observed. This study provides innovative information on the role of oxygen in wine spirit’s ageing, and on chestnut wood effect on wine spirit’s mineral composition.     

Application of Square Wave Anodic Stripping Voltammetry for Determination of Traces of Ti(I) at Carbon Electrodes In Situ Modified with Bi Films

Bismuth films deposited in situ at glassy carbon and carbon film electrodes were tested for the determination of traces of Tl(I) separately and together with Zn(II) and Pb (II), in acetate buffer solution pH 3.7, using square wave anodic stripping voltammetry. Electrochemical impedance spectra in the presence of Tl(I) showed differences between the electrode substrates. The sensitivity to Tl does not depend on the presence of other ions, and was better at carbon film electrodes, although the 2 nmol L^?1 detection limit was independent of electrode substrate. Application to the measurement of Tl(I) in commercial berry juice is demonstrated.     

Electrical study of cathodic activation and relaxation of La0,80Sr0,20MnO3

The effect of cathodic activation of sprayed La_0.8Sr_0.2MnO₃ (LSM) films has been studied by electrochemical spectroscopy impedance (EIS). LSM powder was prepared by a citrate route and X-ray diffraction analyses show a complete LSM crystallization without La₂O₃ or La(OH)₃ as side products. Porosity and grain size estimated from scanning electronic microscopy gave values of 33% and 100 nm, respectively. EIS measurement was performed on a Pt/yttria-stabilized zirconia/LSM cell before and after a cathodic current load (300 mA/cm²) on LSM electrode. The relaxation process, which is time-dependent, has been investigated. A drastic decrease of the electrode resistance was noticed just after applying the cathodic current, but after 9 h at optimized valence configuration in air at 850 °C, the recorded polarization resistance gradually enhanced until it almost reached the initial value. The resulting diagrams have been fitted using a Gerischer associated with a resistor and constant phase elements. This simple method has permitted us to observe that only the electrode interfaces are modified by a cathodic activation and the microstructure remains nearly constant.     

Port wine spectronephelometry

The main purpose of this research was to create a portable equipment capable of measuring colour and turbidity during production of port wine. Actually, human, chemical and colour analysis are performed in key production stages for quality control. Several wine transformation processes are done without any kind of control. By using a fibre optic illuminator with a tungsten/halogen light source and a small spectrometer with fibre optic input, it was possible to perform angular measurements in wine samples. We have adapted these optical devices with a specially designed mechanical equipment which allows the passage of the wine during production. The spectral measurements were acquired in four different angular positions in a bypass of the mechanical support. This way we could determine colour coordinates and spectral transmittance and turbidity for three stages of a Ruby production. The entire equipment assembly had been previously calibrated in terms of colour and turbidity determination. The obtained results are in agreement with wine transformations between measurements, showing a small variation in colour and a high diminishing in spectral turbidity when filtration was performed. Transmittance has also increased after filtration turning the wine more limpid as it should be for human appreciation.