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21.
Site-directed mutagenesis study on the roles of evolutionally conserved aspartic acid residues in human glutathione S-transferase P1-1 总被引:1,自引:0,他引:1
Kong Kwang-Hoon; Inoue Hideshi; Takahashi Kenji 《Protein engineering, design & selection : PEDS》1993,6(1):93-99
The evolutionally conserved aspartyl residues (Asp57, Asp98and Asp152) in human glutathione S-transferase P1-1 were replacedwith alanine by site-directed mutagenesis to obtain the mutants(D57A, D98A and D152A). The replacement of Asp98 with alanineresulted in a decrease of the affinity for S-hexyl-GSH-agarose,a 5.5-fold increase of the KmGHS and a 2.9-fold increase ofthe I50 of S-hexyl-GSH for GSHCDNB conjugation. Asp98seems to participate in the binding of GSH through hydrogenbonding with the -carboxylate of the -glutamyl residue of GSH.The kcat of D98A was 2.6-fold smaller than that of the wild-type,and the pKa of the thiol group of GSH bound in D98A was {smalltilde}0.8 pK units higher than those in the wild-type. Asp98also seems to contribute to the activation of GSH to some extent.On the other hand, most of the kinetic parameters of D57A andD152A were similar to those of the wild-type. However, the thermostabilitiesof D57A and D152A were significantly lower than that of thewild-type. Asp57 and Asp152 seem to be important for maintainingthe proper conformation of the enzyme. 相似文献
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Hydrocracking of benzyl phenyl ether and diphenyl ether has been carried out over a series of iron catalysts (Fe2O3, Fe2O3Al2O3, Fe2O3ZnO, Fe2O3ZrO2, Fe2O3MgO and Fe2O3SiO2) and reference catalysts (, and SiO _Al2O3) to search for active and selective catalysts, and to elucidate the catalyst properties of relevance for CO bond cleavage. Among the iron catalysts, Fe2O3ZnO, Fe2O3ZrO2 and Fe2O3MgO exhibited relatively high activities and selectivities. The important property of catalysts relevant to hydrocracking of the ethers is the ability to accomplish hydrogenation. Acidic properties of the catalysts cause condensation and rearrangement of the reactants. The features of the iron catalysts are compared with those of molybdenum catalysts, and the reaction mechanisms discussed. 相似文献
23.
Hideshi Suzuki Masahiro Ogawa Kenji Hironaka Kunio Ito Hisakazu Sunada 《Drug development and industrial pharmacy》2001,27(9):943-949
Sodium deoxycholate (DCNa) is a bile salt that forms multimolecular inclusion compounds with a variety of organic substances. In this study, complex formulation of DCNa with nifedipine, a poorly water soluble drug, by grinding was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction, differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. A laser diffraction particle size analyzer was also used to determine the particle size distribution curve in solution. When a nifedipine-DCNa (1:2 w/w) mixture coground for 30 min was dispersed into water and a pH 6.8 buffer solution, a semitransparent colloidal solution occurred immediately; 90% of the total particles formed in solution had a diameter less than 600 nm. Both powder X-ray diffraction peaks and DSC endothermic peak of nifedipine crystals were not found for the coground mixture, whereas a new exothermic peak was observed on DSC thermograms. The magnitude of this exothermic peak depended on the weight fraction of DCNa and the grinding time, indicating that nifedipine crystals changed into an amorphous state by complex formation with DCNa during the grinding process. In the FTIR spectrum of the coground mixture, the peaks of aromatic CH out-of-plane bend and dihydropyridine NH stretch of nifedipine were considerably weakened, suggesting that van der Waals interaction may be present between the drug and DCNa molecules. From these results, it is clear that the cogrinding method with DCNa is very useful for the formation of amorphous nifedipine in the solid state and the production of colloidal particles of the drug in solution. 相似文献
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Toru Ikegami Hideyuki Negishi Hideshi Yanase Keiji Sakaki Masayoshi Okamoto Nobuyuki Koura Tsuneji Sano Kenji Haraya Hiroshi Yanagishita 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(8):745-751
Since pervaporation performance of ethanol‐permselective silicalite membrane, which is an aluminum‐free hydrophobic zeolite, in the separation of fermentation broths by yeast are negatively affected by succinic acid, the potential of pervaporation using silicone rubber‐coated silicalite membranes of ethanol fermentation broths, not containing succinic acid, by Zymomonas mobilis was investigated for the reliable production of concentrated bioethanol. In the separation of fermentation broths, the pervaporation performance was influenced by nutrients used for the preparation of fermentation broths. In the separation of a broth prepared with yeast extract, pervaporation performance was greatly compromised by accumulation of a substance(s) having an ultraviolet absorption maximum at approximately 260 nm not only in total flux, but also in permeate ethanol concentration compared to the separation of binary ethanol/water mixtures. When supplying a prepared broth with corn steep liquor without the accumulation of a substance(s) having an ultraviolet absorption maximum at approximately 260 nm, the permeate ethanol concentration did not decrease. Treating the prepared broth with activated carbon was effective in restraining the decrease in total flux. Pervaporation performance is also deteriorated by the adsorption of lactic acid contained in corn steep liquor onto the silicalite crystals. In the separation of ternary mixtures of ethanol/water/lactic acid, accomplished by adjusting the ternary mixtures to pH > 5, more than 90% of the permeation flux in the separation of binary ethanol/water mixtures was obtained, and the permeate ethanol concentration was comparable to that obtained in the separation of binary mixtures. For stably performing pervaporation, it is important to prepare ethanol fermentation broths by Zymomonas mobilis in which lactic acid concentration is as low as possible. Copyright © 2007 Society of Chemical Industry 相似文献
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In laboratory researches and food packing tests, it has been shown that cold rolled steel strip, plated with a thickness of about 0–002 mil (0–05 μ) of chromium and coated with lacquer is a satisfactory material for cans. It is highly resistant to corrosion, especially to sulphur staining, and the lacquer coating remains firmly adherent. In food packing tests with it, the chromium content of the foodstuffs was no greater than it was with tinplate. The chromium plating line is similar in layout to an electrolytic tinning line, but insoluble electrodes are used and the electrolyte contains chromic and sulphuric acids. For high-speed operation with several plating tanks, special screening of part of the cathode is used to obtain a better lustre. 相似文献
28.
Hideshi Hattori 《Topics in Catalysis》2010,53(7-10):432-438
Extensive studies of the cracking catalyst used in the largest process in chemical industries established the research field of solid acid catalysis. Solid acid catalysts are also utilized in various industrial processes. A new concept for acid site generation, Molecular hydrogen-originated protonic acid site, and its characteristics in alkane isomerization are described. 相似文献
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