Mitochondrial hydroxylation of the cyclohexane ring as a result of β-oxidation blockade of a cyclohexyl substituted fatty acid

Among the urinary metabolites of dodecylcyclohexane or cyclohexylacetic acid, the glycine conjugate of 1-hydroxy-cyclohexylacetic acid was identified and its origin studied, using cyclohexylacetic acid as the starting molecule, as it results from β-oxidation of cyclohexyldodecanoic acid produced by terminal oxidation of the alkyl chain of the cycloparaffin. Three hypotheses were tested: (a) hydroxylation by the liver microsomal mixed-function oxidases involved in detoxication mechanisms; (b) hydroxylation by a cyt. P₄₅₀-containing mitochondrial hydroxylase; and (c) β-oxidation blockade after the reaction catalyzed by enoyl-CoA-hydratase. Liver microsomal or mitochondrial fractions were prepared and incubated in the presence of [¹⁴C] cyclohexylacetic acid, glucose-6-phosphate dehydrogenase and a NADPH-producing system. On the other hand, mitochondria were incubated in a suitable respiratory medium with or without cofactors required for ATP production. The reaction products were extracted and analyzed by thin layer radiochromatography and radio gas chromatography. Evidence is given that hydroxylation of cyclohexylacetic acid in position 1 is a mitochondrial step requiring activation in the acyl-CoA form and results from β-oxidation blockade, the cyclohexane ring hindering hydroxyacyl-CoA-dehydrogenase action.     

Fractionation of peat-derived bitumen into oil and asphaltenes

As a continuation of our previous work on the conversion of peat, we have studied the composition of the bitumens obtained through primary hydrogenation with carbon monoxide in the presence of water as the liquid medium. The proportion of oils in the bitumen varies considerably, between 30 and 60%, as a function of the experimental conditions chosen. CO is preferred over H₂ as the hydrogenating gas. Temperature is the most important single variable, with 350–375 ° C as a suitable range for the conversion. Li₂CO₃ favours significantly the conversion to oils even if K₂CO₃ results in a higher bitumen yield. High CO pressures, surprisingly, lower the oil fraction in the bitumen.     

Elaboration et caracterisation de monocristaux de V2O3 par transport en phase vapeur

Single crystals of V₂O₃ are obtained by HCl or TeCl₄ chemical transport method in sealed quartz tubes with temperature gradients of 1050–930°C and 990–900°C respectively. The hexagonal prims are 5 mm long and 1 or 2 mm wide. Both kinds of crystals are characterized by sharp insulator-metal transition at 156 and 137 K respectively, they present a large hysteresis. The sharp decrease in resistivity with increasing temperature is of the order of 10⁸ at the transition.     

Sur les proprietes magnetiques du fluorure K5V3F14 de type chiolite

The magnetic properties of the fluoride K₅V₃F₁₄ of the chiolite type have been investigated on single crystals. The expected ferrimagnetic behaviour has been pointed out, the ordering temperature being 18 ± 1 K. Anisotropy measurements involve that the magnetic moments are parallel to the c axis.     

Etude par diffraction X et microscopie electronique des composes inedits de formule AnBnO3n+2 dans les systems La2Ti2O7CaTiO3, Nd2Ti2O7CaTiO3 et Ca2Nb2O7CaTiO3

New compounds corresponding to the formula A_nB_nO_3n+2 with n = 4,5; 5 and 6 have been found in the two following systems Nd₂Ti₂O₇CaTiO₃ and Ca₂Nb₂O₇CaTiO₃. These compounds have been investigated by electron microscopy. The results obtained are in good agreement with our structural hypothesis.     

Identification of 4-hydroxy-2-nonenal-modified peptides within unfractionated digests using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The lipid peroxidation product 4-hydroxy-2-nonenal (HNE) is generated as a consequence of oxidative stress and can readily react with nucleophilic sites of proteins (e.g., histidine residues), mainly via a Michael addition. The formation of such lipid-protein conjugates can alter protein properties and biological functions, thus leading to highly deleterious effects. The present work describes a rapid (very limited sample preparation) and sensitive (low-femtomole range) procedure to identify HNE-modified peptides (Michael adducts) within unfractionated tryptic digests. The protocol involves the formation of dinitrophenylhydrazones of the Michael adducts, when using 2,4-dinitrophenylhydrazine as reactive matrix, followed by analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). The hydrazone derivatives present high desorption/ionization yield and can thus be preferentially detected compared to unmodified peptides. The MALDI mass spectrum obtained is therefore drastically different from the one obtained with the classical 4-hydroxy-alpha-cyanocinnamic acid matrix. Moreover, the presence of HNE, or more generally speaking carbonylated peptides, could be highlighted by 180 mass units differences (corresponding to the dinitrophenylhydrazone moiety) between these two MALDI mass spectra. Further information (e.g., localization/identification of the modified residues, peptide sequences) could be obtained by performing MALDI postsource decay (or electrospray) MS/MS experiments on the ions of interest.     

Preparation and electrochemical properties of Sr-doped Nd2NiO4 cathode materials for intermediate-temperature solid oxide fuel cells

Cathode materials Nd_2 − xSr_xNiO₄ were prepared by the glycine-nitrate process and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), AC impendence spectroscopy and DC polarization method, respectively. The results show that no reaction occurred between the electrode and the CGO electrolyte at 1100 °C and the electrode formed good contact with the electrolyte after being sintered at 1000 °C for 4 h. The rate-limiting step for oxygen reduction reaction on Nd_1.6Sr_0.4NiO₄ electrode changed with oxygen partial pressure and measurement temperature. The Nd_1.6Sr_0.4NiO₄ electrode gave a polarization resistance of 0.93 Ω cm² at 700 °C in air, which indicates that Nd_2 − xSr_xNiO₄ electrode is a promising cathode material for intermediate-temperature solid oxide fuel cell (IT-SOFC).