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51.
Fumihiko Hasumi Yasumitsu Miyamoto Ichiro Okura 《Applied biochemistry and biotechnology》1995,55(1):1-4
Glutamate synthesis by reductive amination of 2-oxoglutarate was performed by the combination of NADH regeneration system
and glutamate dehydrogenase (GluDH). The conversion of 2-oxoglutamate to glutamate was 98% after 3 h, and the turnover number
of NAD+was 17. 相似文献
52.
Shunroku Tohyama Masaru Kurihara Kojuro Ikeda Naoya Yoda 《Journal of polymer science. Part A, Polymer chemistry》1967,5(10):2523-2534
Fully aromatic polyquinazolinediones (IV) of high molecular weight were obtained by thermal cyclodehydration of aromatic poly(uredio acids) (III) prepared by the polyaddition reaction of 4,4′-diaminobiphenyl-3,3′-dicarboxylic acid (I) with aromatic diisocyanates (II). From the kinetic study of reactions of model systems (anthranilic acid with phenyl isocyanate) in the presence of a variety of basic catalysts, it was established that tertiary amines had the highest catalytic activity for the formation of ureido linkage. The optimum polymerization conditions were determined by the study of reaction variables such as monomer concentration, polymerization temperature, monomer ratio, and catalyst concentration. The effect of polarity and purity of organic solvents and reactants was also studied. 相似文献
53.
A new-type of sol-gel/organic hybrid composite material using gelatin or chitosan with tetramethoxysilane was developed for the bovine serum albumin (BSA)-encapsulated monolithic column for capillary electrochromatography (CEC). The composite monolith was used to immobilize BSA in a fused-silica capillary. The addition of gelatin and chitosan to the alkoxysilane enabled the enantioseparation of Trp. A very small amount of these polymers were effective for the enantioseparation. Especially, the monolithic column prepared from chitosan with tetramethoxysilane showed a high enantioselectivity for Trp enantiomers and the value (alpha' = t2/t1, t1: fast eluted enantiomer, t2: second eluted enantiomer) reached 1.15 on CEC mode. Furthermore, the composite materials exhibited a higher stability compared to the silica sol-gel column. These results showed that the sol-gel/organic hybrid composite was useful as a monolithic matrix for the BSA-encapsulated column for CEC. 相似文献
54.
Ai Suzuki Parasuraman Selvam Tomonori Kusagaya Seiichi Takami Momoji Kubo Akira Imamura Akira Miyamoto 《International journal of quantum chemistry》2005,102(3):318-327
The decomposition reaction dynamics of 2,3,4,4′,5‐penta‐chlorinated biphenyl (2,3,4,4′,5‐PeCB), 3,3′,4,4′,5‐penta‐chlorinated biphenyl (3,3′,4,4′,5‐PeCB), and 2,3,7,8‐tetra‐chlorinated dibenzo‐p‐dioxin (2,3,7,8‐TCDD) was clarified for the first time at atomic and electronic levels, using our novel tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization. The calculation speed of our new method is over 5000 times faster than that of the conventional first‐principles molecular dynamics method. We confirmed that the structure, energy, and electronic states of the above molecules calculated by our new method are quantitatively consistent with those by first‐principles calculations. After the confirmation of our methodology, we investigated the decomposition reaction dynamics of the above molecules and the calculated dynamic behaviors indicate that the oxidation of the 2,3,4,4′,5‐PeCB, 3,3′,4,4′,5‐PeCB, and 2,3,7,8‐TCDD proceeds through an epoxide intermediate, which is in good agreement with the previous experimental reports and consistent with our static density functional theory calculations. These results proved that our new tight‐binding quantum chemical molecular dynamics method with first‐principles parameterization is an effective tool to clarify the chemical reaction dynamics at reaction temperatures. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
55.
Cordonier CE Satake K Atarashi M Kawamoto Y Okamoto H Kimura M 《The Journal of organic chemistry》2005,70(9):3425-3436
[reaction: see text] The reaction of 2-methoxy-3H-azepines, in the presence or absence of a nucleophile, with N-bromosuccinimide (NBS) gave a regioselective 1,4-adduct from which the corresponding 2H-azepine derivatives were formed via base-promoted hydrogen bromide elimination, generally in moderate to quantitative yield. Competitive formation of 4-bromo-2-methoxy-3H-azepine by electrophilic substitutuion or 3H-azepin-2-yl 2H-azepin-2-yl ether by transetherification was minimized at lower reaction temperatures. Quantitative substitution of 2-(2',4',6'-trichlorophenoxy)-2H-azepine derivatives, formed in moderate yield from the respective 3H-azepine and NBS in the presence of 2,4,6-trichlorophenol (TCP), by various nucleophiles gave the corresponding 2-substituted 2H-azepine. Among these nucleophiles were alkanethiol and alkylamine that are not tolerated in the reaction of 3H-azepine and NBS. 相似文献
56.
Fumihiko Hasuni Katsunori Fukuoka Shuichi Adachi Yasumitsu Miyamoto Ichiro Okura 《Applied biochemistry and biotechnology》1996,56(3):341-344
Alanine synthesis by reductive amination of pyruvate was performed by the combination of NADH regeneration system and alanine
dehydrogenase (AlaDH). The conversion of pyruvate to alanine was 99% after 1 h. Leucine synthesis was also carried out by
the combination of NADH regeneration system and leucine dehydrogenase (LeuDH). The conversion of 4-methyl-2-oxovalerate to
leucine was 60% after 1.5 h. 相似文献
57.
Rate constants for hydrogen atom abstraction by methyl radicals in methanol glasses have been measured from 100 to 15 K. The Arrhenius plot is nonlinear and the reaction rate constant appears to reach a limiting value below 40 K. The results are discussed in terms of simple models for quantum-mechanical tunneling in the solid state at low temperatures. Assuming that the methyl group rotation in methanol brings about a merging of the energy level distribution at the potential barrier, the observation of temperature-independent rate constants below 40 K may be attributable to a freezing out of this rotation such that tunneling occurs only from the zero-point vibrational level. 相似文献
58.
Comparison of PAMAM-Au and PPI-Au nanocomposites and their catalytic activity for reduction of 4-nitrophenol 总被引:4,自引:0,他引:4
Dendrimer-Au nanocomposites are prepared in aqueous solutions using poly(amidoammine)dendrimers (PAMAM) (generation 2, 3, and 5) and poly(propyleneimine)dendrimers (PPI)(generation 2, 3, and 4) by wet chemical NaBH(4) method. The Au nanoparticles thus obtained are 2-4 nm in diameter for both dendrimers and no generation dependence on the particle size is observed, whereas the generations of the dendrimers are increased as stabilization of Au-nanoparticles is achieved with lower dendrimer concentrations. Studies of the reduction reaction of 4-nitrophenol using these nanocomposites show that the rate constants for the PAMAM dendrimers (generations 2 and 3) are higher than those for the PPI dendrimers (generations 2 and 3), while a distinct difference in the rate constants is not seen for the PAMAM dendrimer (generation 5) or the PPI dendrimer (generation 4). In addition, the rate constants for the reduction of 4-nitrophenol involving all the dendrimers decrease with increases in dendrimer concentrations. 相似文献
59.
cis-2-Alkylcyclohexanols are obtained stereoselectively upon irradiation of a mixture of cyclohexene and the corresponding trialkylborane in the presence of p-xylene as a sensitizer and upon the successive oxidation of the photolysate with alkaline H2O2. The similar reaction of 1-ethylcyclohexene yields 2,2-dialkylcyclohexanols. Cycloheptene also reacts with the boranes to afford cis-2-alkylcycloheptanols. These reactions are explained by assuming the highly strained trans-cyclohexene or -heptene to be the reactive species. Photochemically produced trans-cyclo-oct-2-enone and cis,trans-cyclo-octa-2,7-dienone react thermally with the bora e to give 3-alkylcyclo-octanone and cis-7-alkylcyclo-oct-2-enone, respectively. Photoreactions of acridine with the boranes result in reductive alkylation, affording 9-alkylacridans in fairly good yields. 相似文献
60.
Noncatalytic reaction pathways and rates of dimethyl ether (DME) in supercritical water are determined in a tube reactor made of quartz according to liquid- and gas-phase 1H and 13C NMR observations. The reaction is studied at two concentrations (0.1 and 0.5 M) in supercritical water at 400 degrees C and over a water-density range of 0.1-0.6 g/cm3. The supercritical water reaction is compared with the neat one (in the absence of solvent) at 0.1 M and 400 degrees C. DME is found to decompose through (i) the proton-transferred fragmentation to methane and formaldehyde and (ii) the hydrolysis to methanol. Formaldehyde from reaction (i) is consecutively subjected to four types of redox reactions. Two of them proceed even without solvent: (iii) the unimolecular proton-transferred decarbonylation forming hydrogen and carbon monoxide and (iv) the bimolecular self-disproportionation generating methanol and carbon monoxide. When the solvent water is present, two additional paths are open: (v) the bimolecular self-disproportionation of formaldehyde with reactant water, producing methanol and formic acid, and (vi) the bimolecular cross-disproportionation between formaldehyde and formic acid, yielding methanol and carbonic acid. Methanol is produced through the three types of disproportionations (iv)-(vi) as well as the hydrolysis (ii). The presence of solvent water decelerates the proton-transferred fragmentation of DME; the rate constant is reduced by 40% at 0.5 g/cm3. This is caused by the suppression of low-frequency concerted motion corresponding to the reaction coordinate for the simultaneous C-O bond scission and proton transfer from one methyl carbon to the other. In contrast to the proton-transferred fragmentation, the hydrolysis of DME is markedly accelerated by increasing the water density. The latter becomes more important than the former in supercritical water at densities greater than 0.5 g/cm3. 相似文献