Search results for "Hydrogen"
showing 10 items of 4254 documents
Purification and spectroscopic studies on catechol oxidases from Lycopus europaeus and Populus nigra: evidence for a dinuclear copper center of type …
1999
We purified two catechol oxidases from Lycopus europaeus and Populus nigra which only catalyze the oxidation of catechols to quinones without hydroxylating tyrosine. The molecular mass of the Lycopus enzyme was determined to 39,800 Da and the mass of the Populus enzyme was determined to 56,050 Da. Both catechol oxidases are inhibited by thiourea, N-phenylthiourea, dithiocarbamate, and cyanide, but show different pH behavior using catechol as substrate. Atomic absorption spectrosopic analysis found 1.5 copper atoms per protein molecule. Using EPR spectroscopy we determined 1.8 Cu per molecule catechol oxidase. Furthermore, EPR spectroscopy demonstrated that catechol oxidase is a copper enzym…
Reduction of tris(benzene-1,2-dithiolate)molybdenum(VI) by hydroxide ions in dry tetrahydrofuran solution.
2001
Tris(benzene-1,2-dithiolate)molybdenum(VI) reacts rapidly and quantitatively with tetrabutylammonium hydroxide to yield the corresponding Mo(V) and Mo(IV) complexes and hydrogen peroxide; the reaction has been executed in dry tetrahydrofuran where the reaction rate shows a fair dependence on complex and OH2 concentrations. Cervilla Avalos, Antonio, Antonio.Cervilla@uv.es ; Perez Pla, Francisco, Francisco.Perez@uv.es ; Llopis Jover, Elisa, Elisa.Llopis@uv.es
The selective oxidative dehydrogenation of ethane over hydrothermally synthesised MoVTeNb catalysts
2002
Mo–V–Te–Nb metal oxide catalysts prepared by hydrothermal synthesis and heat-treated in N2 at high temperatures (600–700 °C) show high activity and selectivity for the oxidative dehydrogenation of ethane to ethene. Yields of ethene of 75% have been obtained at 400 °C on the best catalysts. Dejoz Garcia, Ana Maria, Ana.M.Dejoz@uv.es
Novel inhibitors of mitochondrial respiratory chain: endoperoxides from the marine tunicate Stolonica socialis.
2001
The Mediterranean tunicate Stolonica socialis contains a new class of powerful cytotoxic acetogenins, generically named stolonoxides. In this paper, which also details the isolation and chemical characterization of a minor component (3a) of the tunicate extract, we report the potent inhibitory activity (IC(50) < 1 microM) of stolonoxides (1a and 3a) on mitochondrial electron transfer. The compounds affect specifically the functionality of complex II (succinate:ubiquinone oxidoreductase) and complex III (ubiquinol:cytochrome C oxidoreductase) in mammalian cells, thereby causing a rapid collapse of the whole energetic metabolism. This result, which differs from the properties of similar known…
Kinetic characterization of mitochondrial complex I inhibitors using annonaceous acetogenins
1999
The NADH:ubiquinone oxidoreductase (complex I) of the mitochondrial respiratory chain is by far the largest and most complicated of the proton-translocating enzymes involved in the oxidative phosphorylation. Many clues regarding the electron pathways from matrix NADH to membrane ubiquinone and the links of this process with the translocation of protons are highly controversial. Different types of inhibitors become valuable tools to dissect the electron and proton pathways of this complex enzyme. Therefore, further knowledge of the mode of action of complex I inhibitors is needed to understand the underlying mechanism of energy conservation. This study presents for the first time a detailed …
On the Deactivation Mechanisms of Adenine–Thymine Base Pair
2012
In this contribution, the multiconfigurational second-order perturbation theory method based on a complete active space reference wave function (CASSCF/CASPT2) is applied to study all possible single and double proton/hydrogen transfers between the nucleobases in the adenine-thymine (AT) base pair, analyzing the role of excited states with different nature [localized (LE) and charge transfer (CT)], and considering concerted as well as step-wise mechanisms. According to the findings, once the lowest excited states, localized in adenine, are populated during UV irradiation of the Watson-Crick base pair, the proton transfer in the N-O bridge does not require high energy in order to populate a …
The Cth2 ARE-binding protein recruits the Dhh1 helicase to promote the decay of succinate dehydrogenase SDH4 mRNA in response to iron deficiency
2008
Iron is an essential nutrient that participates as a redox co-factor in a broad range of cellular processes. In response to iron deficiency, the budding yeast Saccharomyces cerevisiae induces the expression of the Cth1 and Cth2 mRNA-binding proteins to promote a genome-wide remodeling of cellular metabolism that contributes to the optimal utilization of iron. Cth1 and Cth2 proteins bind to specific AU-rich elements within the 3'-untranslated region of many mRNAs encoding proteins involved in iron-dependent pathways, thereby promoting their degradation. Here, we show that the DEAD box Dhh1 helicase plays a crucial role in the mechanism of Cth2-mediated mRNA turnover. Yeast two-hybrid experim…
Glyceraldehyde-3-phosphate dehydrogenase regulates endothelin-1 expression by a novel, redox-sensitive mechanism involving mRNA stability
2008
17 pages.-- PMID: 18809573 [PubMed].-- Printed version published on Dec 2008.
Sulfate-Templated 2D Anion-Layered Supramolecular Self-Assemblies
2019
Summary Using solution and solid-state analyses, we demonstrate that the tripodal N-methylated(1,3,5-benzene-tricarboxamide)-tris(phenylurea) BTA ligands, possessing urea functionalities in the meta position, are able to form extended self-assembly 2D networks via hydrogen bonding templated by sulfate (SO42–). The divergence of the urea binding sites confers a propeller-like conformation to the ligands and is key to formation of the self-assemblies. Studies in solution and in the solid state as well as scanning electron microscopy (SEM) on the self-assembly properties of the ligands showed that the convergence also leads to the formation of hierarchical structures, including porous films an…
Die Dissoziationskonstanten von 2,2?-Dihydroxydiphenylmethanderivaten
1973
The pK-values of the first and second degree of dissociation of 2.2′-dihydroxy-5-methyl-3′.5′-dinitro-diphenylmethane, 2.2′-dihydroxy-5-methyl-5′-nitro-diphenylmethane and 2.2′-dihydroxy-5.5′-dimethyl-3′-nitro-diphenylmethane were determined in aqueous solution at 25°C spectrophotometrically. Comparing the observed pK-values with those of 2-methyl-4.6-dinitrophenol, 2-methyl-4-nitrophenol, 2.4-dimethyl-6-nitro-phenol and 2.4-dimethylphenol, we found a decrease of the values of pK1 and an increase of pK2. We explain this by the formation of an intramolecular hydrogen bridge which stabilizes the anion of the half dissociated form. This assumption is supported by the UV spectra.