Anhydrase carbonique

Résumé

L'anhydrase carbonique est une enzyme présente à la surface plasmique intracellulaire (liée à l'échangeur anionique AE1 Cl/HCO3) des globules rouges (ou hématies ou encore érythrocytes) qui transforme le en et inversement. La plupart des anhydrases carboniques contiennent un atome de zinc. C'est une des enzymes les plus rapides connues. Équation : + − + . Dans les reins, elle sert à libérer les protons . Dans les os compacts, l'anhydrase carbonique permet de maintenir les lacunes de Howship dans un milieu acide (pH=4,5) grâce à un apport en H+ Notes et références Catégorie:EC 4.2.1 Catégorie:Sang Catégorie:Métalloprotéine

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EPFL2005

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The measurements obtained were used to investigates the methanol synthesis reaction from pure carbon dioxide and hydrogen over binary (CuO/ZrO2) and ternary supported catalysts (CuO/ZnO/Al2O3). A comparison of different catalysts is presented. The influence of the most important reaction parameters, i.e. temperature, pressure, space velocity and feed gas composition is examined at moderate temperatures (≤ 300 °C) and pressures (≤ 20 bar). The influence of the partial pressures of hydrogen, carbon dioxide, carbon monoxide, water and methanol are studied in detail with the most efficient catalyst. According to the results, water has a decisive effect on the catalyst activity and performance. The measured results were used to derive a possible Langmuir-Hinshelwood kinetic model of the methanol synthesis reaction. The catalyst surface is analyzed by in situ diffuse reflectance Fourier transform infrared spectroscopy. The identification and evolution of intermediates on CuO/ZnO/Al2O3 catalysts confirm that the reaction proceeds by prior formation of the carbonate on the copper, followed by hydrogenation of the carbonate to the formate and thereafter to methoxy and methanol. For CuO/ZrO2 catalysts results demonstrate that the methanol formation occurs via π – bound formaldehyde and methoxy. Responses of sine shape variation applied to the reactants are also examined. The conversion of CO2 with hydrogen to methanol is investigated in dielectric-barrier discharges with and without catalysts at low temperatures (≤ 100 °C) and pressures (≤ 10 bar). The combination of discharges and catalysts lower the activation energy of the reaction resulting in a decrease in the catalyst optimum temperature. The presence of the catalyst in the discharge increases the methanol yield and selectivity by more than a factor of 10. Electrochemical reduction of carbon dioxide is briefly investigated by using TiO2/Ni complex and TiO2/Ru complex thin film electrodes. A considerable decrease in overvoltage is achieved together with respectable current densities.

EPFL1998

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Modulating protein activity using tethered ligands with mutually exclusive binding sites

Rudolf Griss, Kai Johnsson, Alberto Schena

The possibility to design proteins whose activities can be switched on and off by unrelated effector molecules would enable applications in various research areas, ranging from biosensing to synthetic biology. We describe here a general method to modulate the activity of a protein in response to the concentration of a specific effector. The approach is based on synthetic ligands that possess two mutually exclusive binding sites, one for the protein of interest and one for the effector. Tethering such a ligand to the protein of interest results in an intramolecular ligand–protein interaction that can be disrupted through the presence of the effector. Specifically, we introduce a luciferase controlled by another protein, a human carbonic anhydrase whose activity can be controlled by proteins or small molecules in vitro and on living cells, and novel fluorescent and bioluminescent biosensors.

Nature Publishing Group2015

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