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New Assay Method Based on Raman Spectroscopy for Enzymes Reacting with Gaseous Substrates
摘要： Enzyme activity is typically assayed by quantitatively measuring the initial and final concentrations of the substrates and/or products over a defined time period. For enzymatic reactions involving gaseous substrates, the substrate concentrations can be estimated either directly by gas chromatography or mass spectrometry, or indirectly by absorption spectroscopy, if the catalytic reactions involve electron transfer with electron mediators that exhibit redox-dependent spectral changes. We have developed a new assay system for measuring the time course of enzymatic reactions involving gaseous substrates based on Raman spectroscopy. This system permits continuous monitoring of the gas composition in the reaction cuvette in a non-invasive manner over a prolonged time period. We have applied this system to the kinetic study of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F. This enzyme physiologically catalyzes the reversible oxidation of H2 and also possesses the non-physiological functions of H/D exchange and nuclear spin isomer conversion reactions. The proposed system has the additional advantage of enabling us to measure all of the hydrogenase-mediated reactions simultaneously. Using the proposed system, we confirmed that H2 (the fully exchanged product) is concomitantly produced alongside HD by the H/D exchange reaction in the D2/H2O system. Based on a kinetic model, the ratio of the rate constants of the H/D exchange reaction (k) at the active site and product release rate (kout) was estimated to be 1.9±0.2. The proposed assay method based on Raman spectroscopy can be applied to the investigation of other enzymes involving gaseous substrates.
关键词： kinetic experiment,H/D exchange reaction,quantitative analysis of gaseous substrates,Raman spectroscopy,non-invasive measurement,[NiFe] hydrogenase
更新于2025-09-23 15:23:52
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Formation of zirconia precursor nanoplates mediated by ionic liquid and transformation to monoclinic ZrO <sub/>2</sub> nanostructures
摘要： The [Zr(OH)5]– imidazolium complex was used to synthesize a zirconia precursor with plate-like nanostructure hydrolyzed under strong acid conditions, which was characterized by means of powder X-ray diffraction, thermogravimetric-differential scanning calorimetry, Fourier transform infrared spectroscopy, Raman spectroscopy, elemental analysis, inductively coupled plasma and electronic differential system. The zirconia precursor can be transformed to monoclinic ZrO2 by annealing at a temperature above 400 °C. With the increasing of the curing temperature, it tended to give rise to porous ZrO2 nanostructures.
关键词： Zirconia precursor,Zirconium oxide,Anion exchange reaction,Nanoplate,Ionic liquid
更新于2025-09-23 15:22:29
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Fabrication and optimization of nanocube mixed halide perovskite films for solar cell application
摘要： In this article, we report the tailoring of nanostructured mixed halide perovskite MAPb(I1-xBrx)3 films with tunable band gap fabricated by anion exchange reaction. In this process, we used PbBr2 and methyl ammonium iodide (MAI) in order to fabricate mixed halide perovskite films. We have observed an uncommon shape transformation from nanocube-hollow tetraoids-nanocubes/plate. The underlying mechanism of shape transformation was discussed based on experimental results. The driving force for such shape transformation is combined effect of anion exchange reaction between I? and Br? at the solid/liquid interface of PbBr2 and MAI, and mechanical driving force exerted by the spin coating process. The shape transformation is highly reproducible, verified by two step process, dipping as well as spinning process. The best performing device using the nanostructured perovskite films in a device architecture FTO/TiO2/MAPb(I1-xBrx)3/Spiri-OMeTAD/Au shows a current density (Jsc,) of 23.58 mA/cm2, open circuit voltage (Voc) of 0.891 V and fill factor (FF) of 0.608, with a power conversion efficiency (η) of 12.79% in forward sweep. In reverse sweep, the device shows the Jsc (mA/cm2), Voc (V), FF, and η (%) are 23.852, 0.891, 0.716 and 15.237, respectively.
关键词： Nanostructured perovskite films,Anion exchange reaction,Shape transformation,Mixed halide perovskite films,Perovskite solar cell
更新于2025-09-19 17:13:59
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Some Aspects of Metal Exchange Between Cadmium Porhyrinate Octa-(4-bromophenyl)porphyrin and Cobalt Chloride in Organic Solvents
摘要： The metal-exchange reaction between Cd(II) octa-(4-bromophenyl)porphyrinate and cobalt chloride in DMF and DMSO was studied by UV-Vis spectroscopy. The kinetic parameters of the metal-exchange reaction were calculated. A possible mechanism of the reaction was established. An effect of the nature of the solvent and metal salt on the reaction rate was revealed. Comparative analysis of the apparent rate constants of the metal exchange reaction between CoCl2 and Cd(II) octa-(4-bromophenyl)porphyrinates and Cd(II) octa-(4-bromophenyl)tetraazaporphyrinate in DMF and DMSO was performed.
关键词： Co(III) octa-(4-bromophenyl)porphyrinate,Cd(II) octa-(4-bromophenyl)porphyrinate,metal-exchange reaction,Co(II) octa-(4-bromophenyl)porphyrinate
更新于2025-09-10 09:29:36