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排序方式: 共有402条查询结果,搜索用时 234 毫秒
1.
Dr. Nozomi Mihara Dr. Yasuyuki Yamada Dr. Hikaru Takaya Prof. Yasutaka Kitagawa Dr. Kazunobu Igawa Prof. Katsuhiko Tomooka Prof. Hiroshi Fujii Prof. Kentaro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3369-3375
Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 5+, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 5+ catalyzed ethane oxidation in the presence of H2O2 at a relatively low temperature. The site-selective complexation of 3 5+ with an additional anionic porphyrin (TPPS4−) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 5+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4− to 3 5+ enhanced the catalytic activity. 相似文献
2.
A flow-injection system for the determination of 3-hydroxybutyrate in serum is described. 3-Hydroxybutyrate dehydrogenase is immobilized on poly(vinyl alcohol) beads and incorporated in a flow-injection system. 1-Methoxy-5-methylphenazinium methylsulphate reacts with enzymatically generated NADH to give H2O2, which is detected chemiluminometrically with the reaction of luminol and hexacynoferrate(III). Serum is diluted and filtered through an ultrafiltration membrane. The system responds linearly to injected samples (80 μl) in the concentration range 0.5–300 μM; the detection limit is 0.1 μM. The within-day relative standard deviation (n = 90) for 58 μM 3-hydroxybutyrate in serum is 0.8%. The maximum throughout is 20 samples per hour. The immobilized enzyme is stable for at least 1 month. 相似文献
3.
Two novel aromatic glycosides were obtained from Puerariae Radix and their chemical structures were characterized. 相似文献
4.
Furusawa N 《Journal of chromatographic science》2002,40(6):355-358
A simplified determining method for the routine monitoring of residual amprolium in edible chicken tissues (muscle and liver) is developed using a high-performance liquid chromatographic (HPLC) method with a photodiode-array detector after sample cleanup by an Ultrafree-MC/PL centrifugal ultrafiltration unit. For the HPLC determination and identification, a Mightysil RP4 GP column and a mobile phase of an ethanol-5 mM 1-heptanesulfonic acid sodium salt solution (35:65, v/v) using an ion-pairing system with a photodiode-array detector are used. Average recoveries (spiked at 0.3-3.0 microg/g) are > 90%. The inter- and intravariabilities are 1.9-2.4%. The limits of quantitation are 0.22 microg/g for muscle and 0.25 microg/g for liver. The total time and solvent required for the analysis of one sample are < 20 min and < 2 mL of ethanol, respectively. No toxic solvents and regents are used. 相似文献
5.
Simplified high-performance liquid chromatographic determination of residual amprolium in edible chicken tissues 总被引:1,自引:0,他引:1
Furusawa N 《Journal of chromatographic science》2002,40(7):355-358
A simplified determining method for the routine monitoring of residual amprolium in edible chicken tissues (muscle and liver) is developed using a high-performance liquid chromatographic (HPLC) method with a photodiode-array detector after sample cleanup by an Ultrafree-MC/PL centrifugal ultrafiltration unit. For the HPLC determination and identification, a Mightysil RP-4 GP column and a mobile phase of an ethanol-5 mM 1-heptanesulfonic acid sodium salt solution (35:65, v/v) using an ion-pairing system with a photodiode-array detector are used. Average recoveries (spiked at 0.3-3.0 microg/g) are > 90%. The inter- and intravariabilities are 1.9-2.4%. The limits of quantitation are 0.22 microg/g for muscle and 0.25 microg/g for liver. The total time and solvent required for the analysis of one sample are < 20 min and < 2 mL of ethanol, respectively. No toxic solvents and regents are used. 相似文献
6.
A catalytic photometric method with a flow-injection system is described for the determination of 9,10-phenanthrenequinone. It is based on the catalytic effect of 9,10-phenanthrenequinone on the redox reaction of 1,2-dinitrobenzene with formaldehyde under alkaline conditions. 9,10-Phenanthrenequinone at the 5.0 x 10(-8)-5.0 x 10(-6)M level can be determined at a rate of 20 samples/hr. The detection limit is 1.0 x 10(-8)M (40 pg in a 10-microl injection). 相似文献
7.
Immobilized enzymes were used as column reactors in a high-performance liquid chromatographic system for the specific detection of N-acetyl branched-chain amino acids (AcBCAs) such as N- acetyl- l -valine (AcVal), N- acetyl- l -leucine (AcLeu) and N- acetyl- l -isoleucine (AcIle). Aminoacylase and leucine dehydrogenase were immobilized onto poly(vinyl alcohol) beads. The AcBCAs were separated as three peaks on a Capcell C(1) SG120 column with 0.03M phosphate buffer (pH 8.0). Aminoacylase was capable of hydrolysing the AcBCAs to amino acids, which react with beta-nicotinamide adenine dinucleotide (NAD(+)) in the presence of leucine dehydrogenase. The reduced nicotinamide adenine dinucleotide (NADH) produced was monitored fluorimetrically. The calibration graphs were linear from 4 to 200muM for AcVal and AcLeu, and from 5 to 300muM for AcIle; detection limits for AcVal, AcLeu and AcIle were 2, 2 and 3muM, respectively. The immobilized aminoacylase reactor should be renewed every 5 days owing to a poor stability of aminoacylase. 相似文献
8.
Takaya Y Kikuchi H Terui Y Komiya J Furukawa KI Seya K Motomura S Ito A Oshima Y 《The Journal of organic chemistry》2000,65(4):985-989
For the elucidation of the diversity of secondary metabolites of Dictyostelium cellular slime molds, we investigate the constituent of three species of slime molds. From the methanol extract of their fruit bodies, we obtained three novel compounds, dictyopyrone A (1) and B (2) from D. discoideum and D. rhizoposium and dictyopyrone C (3) from D. longosporum. They possess a unique alpha-pyrone moiety with a side chain at the C-3 position. Their relative structures were elucidated by spectral means, and the absolute configuration was confirmed by asymmetric synthesis of 1. Since these compounds were obtained from different species of Dictyostelium slime molds, they may be a type of compound common to this genus. 相似文献
9.
Kikuchi H Saito Y Komiya J Takaya Y Honma S Nakahata N Ito A Oshima Y 《The Journal of organic chemistry》2001,66(21):6982-6987
We investigated the constituents of Dictyostelium discoideum to clarify the diversity of secondary metabolites of Dictyostelium cellular slime molds and to explore biologically active substances that could be useful in the development of novel drugs. From a methanol extract of the multicellular fruit body of D. discoideum, we isolated two novel amino sugar analogues, furanodictine A (1) and B (2). They are the first 3,6-anhydrosugars to be isolated from natural sources. Their relative structures were elucidated by spectral means, and the absolute configurations were confirmed by asymmetric syntheses of 1 and 2. These furanodictines potently induce neuronal differentiation of rat pheochromocytoma (PC-12) cells. 相似文献
10.
A simple and selective method is presented for the determination of aliphatic amino acids such as L-alanine, L-valine, L-isoleucine and L-leucine in serum using HPLC with detection by co-immobilized alanine dehydrogenase/leucine dehydrogenase post-column reactor and fluorimeter. The enzymes were simultaneously immobilized on chitosan beads. The separation was achieved by means of an ods column with elution with phosphate buffer (pH 7.0). The system gave linear responses over two orders of magnitude and detection limits at 1-2muM levels. 相似文献