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排序方式: 共有107条查询结果,搜索用时 15 毫秒
31.
Hata K Hamamoto H Shiozaki Y Kita Y 《Chemical communications (Cambridge, England)》2005,(19):2465-2467
The oxidation of non-phenolic alkanoic acid derivatives to oxygen heterocycles was investigated; a new oxidative route to dienone lactones has been developed using a combination of hypervalent iodine(III) reagent, phenyliodine(III) bis(trifluoroacetate)(PIFA), and heteropoly acid (HPA). 相似文献
32.
Solvated cobalt(II) ions in neat 1,3-propanediamine (tn) and n-propylamine (pa) have been characterized by electronic absorption spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The equilibrium between tetrahedral and octahedral geometry for cobalt(II) ion has been observed in a neat pa solution, but not in neat diamine solutions such as tn and ethylenediamine (en). The thermodynamic parameters and equilibrium constant at 298 K for the geometrical equilibrium in pa were determined to be DeltaH degrees = -36.1 +/- 2.3 kJ mol(-1), DeltaS degrees = -163 +/- 8 J mol(-1) K(-1), and K(298) = 6.0 x 10(-3) M(-2), where K = [Co(pa)(6)(2+)]/{[Co(pa)(4)(2+)][pa](2)}. The equilibrium is caused by the large entropy gain in formation of the tetrahedral cobalt(II) species. The solvent exchange of cobalt(II) ion with octahedral geometry in tn and pa solutions has been studied by the (14)N NMR line-broadening method. The activation parameters and rate constants at 298 K for the solvent exchange reactions are as follows: DeltaH() = 49.3 +/- 0.9 kJ mol(-1), DeltaS() = 25 +/- 3 J mol(-1) K(-1), DeltaV() = 6.6 +/- 0.3 cm(3) mol(-1) at 302.1 K, and k(298) = 2.9 x 10(5) s(-1) for the tn exchange, and DeltaH() = 36.2 +/- 1.2 kJ mol(-1), DeltaS() = 35 +/- 6 J mol(-1) K(-1), and k(298) = 2.0 x 10(8) s(-1) for the pa exchange. By comparison of the activation parameters with those for the en exchange of cobalt(II) ion, it has been confirmed that the kinetic chelate strain effect is attributed to the large activation enthalpy for the bidentate chelate opening and that the enthalpic effect is smaller in the case of the six-membered tn chelate compared with the five-membered en chelate. 相似文献
33.
Kayoko Iguchi Yoshito Oshima Seiichiro Koda 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):439-444
The laser-induced oxidation of ethane by O2 at 318 K was investigated with varying the pressure between 12–91 atm. The reaction condition was regarded as the supercritical phase above 50–60 atm, depending on the O2 fraction. Ethanol, acetaldehyde, and CO2 were mainly produced at any reaction conditions, together with small amounts of C1 compounds and formic esters. The kinetic discussion for the time dependence indicated that the consecutive photolysis of primary products takes place during the subsequent laser irradiation period. The branching ratio to CO2 formation in the primary process in the supercritical phase is much smaller than that in the gas phase, and the selectivities for ethanol and acetaldehyde show a discontinuous change near the critical point. These facts show that the supercritical phase affects this complex radical reaction system. The primary photoabsorption process is also discussed. 相似文献
34.
A novel method for the assay of alpha-glucosidase inhibitory activity using a multi-channel oxygen sensor. 总被引:3,自引:0,他引:3
Kiyoshi Matsumoto Kayoko Takemata Kiyofumi Takayama Kanthi J M Abesundara Toshiro Matsui Hideo Katayama 《Analytical sciences》2002,18(12):1315-1319
The quantification of glucose by using a multi-channel dissolved oxygen (DO) meter (DOX96) with immobilized glucose oxidase (GOD) and mutarotase (MUT) was performed. An evaluation of the inhibitory activities for alpha-glucosidase (AGH) by modifying our batch-type pseudo-in vivo assay system [Oki et al.; Biol Pharm. Bull., 2000, 232, 1084] was also performed using a DOX96. When 45 U/well GOD and 18.75 U/well MUT were immobilized on the surface of a gelatin membrane on the electrodes, the response shown by the decrease percent of DO (%) obtained with 8 electrode wells in the same row was linear with the glucose concentration up to 3.3 mM and a correlation coefficient larger than 0.9. To estimate the AGH inhibitory activity, AGH-immobilized Sepharose supports in the well of a silent screen plate were used. The IC50 values of acarbose and 1-deoxynojirimycin, a medicinal inhibitor for diabetes, were 0.70 +/- 0.08 microM and 0.40 +/- 0.13 microM, respectively, and coincided well with those by a pseudo-in vivo assay. 相似文献
35.
Kayoko Minakata Hideki Nozawa Itaru Yamagishi Kunio Gonmori Masako Suzuki Koutaro Hasegawa Amin Wurita Kanako Watanabe Osamu Suzuki 《Analytical and bioanalytical chemistry》2014,406(5):1331-1338
A rapid determination method is presented for gold (Au3+) and platinum (Pt4+) in tissues using matrix-assisted laser desorption ionization quadrupole time-of-flight mass spectrometry (MALDI-Q-TOF-MS). Au and Pt ions in wet-ashed tissue solution were reacted with diethyldithiocarbamate (DDC), and the resulting chelate complex ions Au(DDC)2 + and Pt(DDC)3 + were detected by MALDI-Q-TOF-MS using α-cyano-4-hydroxycinnamic acid as a matrix. The limit of detection (LOD) was 0.8 ng/g tissue and the quantification range was 2–400 ng/g for Au, and the LOD was 6 ng/g tissue and the quantification range was 20–4,000 ng/g for Pt. The Pt levels detected by MALDI-Q-TOF-MS in several tissues of a patient overdosed with cisplatin were nearly the same as those detected by flow-injection electrospray ionization mass spectrometry. The LODs of Au and Pt were 0.04 pg per well (sample spot) and 0.3 pg per well, respectively. To our knowledge, this is the first attempt to quantify Au3+ and Pt4+ ions in tissues by MALDI-Q-TOF-MS.
A rapid determination method is presented for gold and platinum in tissues using matrix-assisted laser desorption ionization quadrupole time-of-flight mass spectrometry (MALDI-Q-TOF-MS). Au and Pt ions in wet-ashed tissue solution were reacted with diethyldithiocarbamate (DDC), and the resulted chelate complex ions Au(DDC)2 + and Pt(DDC)3 + were detected using α-cyano-4-hydroxycinnamic acid as a matrix. 相似文献
36.
Synthesis and properties of optically active 1,3-diols and their derivatives as chiral dopants for ferroelectric liquid crystals 总被引:1,自引:0,他引:1
Tetsuo Kusumoto Ken-Ichi Sato Kumiko Ogino Tamejiro Hiyama Sadao Takehara Masashi Osawa Kayoko Nakamura 《Liquid crystals》1993,14(3):727-732
New chiral dopants β-hydroxy ketones 1, 1,3-diols 2, 1,3-dioxanes 3 and 1,3-dioxan-2-ones 4 were designed and synthesized. Reaction of (R)-1,2-epoxyoctane with carbanions derived from 2-(4-substituted phenyl)-1,3-dithianes followed by hydrolysis of the resulting hydroxy dithianes afforded 1. Reduction of 1 gave the diols 2, which yielded 3 upon acetalization and 4 upon carbonation. The syn isomers of 2, 3, and 4 exhibited larger spontaneous polarizations, when applied as chiral dopants, than the anti isomers or hydroxy ketones 1. 相似文献
37.
Chie Kojima Mei Sawada Ikuhiko Nakase Akikazu Matsumoto 《Macromolecular bioscience》2023,23(11):2300139
T-cells play critical roles in various immune reactions, and genetically engineered T-cells have attracted attention for the treatment of cancer and autoimmune diseases. Previously, it is shown that a polyamidoamine dendrimer of generation 4 (G4), modified with 1,2-cyclohexanedicarboxylic anhydride (CHex) and phenylalanine (Phe) (G4-CHex-Phe), is useful for delivery into T-cells and their subsets. In this study, an efficient non-viral gene delivery system is constructed using this dendrimer. Ternary complexes are prepared using different ratios of plasmid DNA, Lipofectamine, and G4-CHex-Phe. A carboxy-terminal dendrimer lacking Phe (G3.5) is used for comparison. These complexes are characterized using agarose gel electrophoresis, dynamic light scattering, and ζpotential measurements. In Jurkat cells, the ternary complex with G4-CHex-Phe at a P/COOH ratio of 1/5 shows higher transfection activity than other complexes, such as binary and ternary complexes with G3.5, without any significant cytotoxicity. The transfection efficiency of the G4-CHex-Phe ternary complexes decreases considerably in the presence of free G4-CHex-Phe and upon altering the complex preparation method. These results suggest that G4-CHex-Phe promotes the cellular internalization of the complexes, which is useful for gene delivery into T-cells. 相似文献
38.
Improved selectivity for the analysis of maternal serum and cord serum for polyfluoroalkyl chemicals
Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid, two of the most widely studied polyfluoroalkyl chemicals (PFCs), can cross the placenta. Therefore, data on the exposure to PFCs of the very young are needed to evaluate the potential health effects associated with such exposure. Human serum, especially serum collected from pregnant women and cord serum, may contain endogenous components that can interfere in the separation by high performance liquid chromatography (HPLC) of PFOS and another PFC of interest, perfluorohexane sulfonic acid (PFHxS), from other serum biomolecules. The presence of such interferences may prevent the adequate quantification of PFOS and PFHxS in cord serum or serum collected from pregnant women, and potentially hinder the assessment of gestational exposure to these important PFCs using biomonitoring. We have modified our on-line solid phase extraction-HPLC-isotope dilution-tandem mass spectrometry analytical method for measuring PFCs in serum and developed an approach that allows for the elimination of these potential interferences without compromising analytical sensitivity and throughput. The combination of acetonitrile as the HPLC mobile phase organic solvent and a Betasil C8 HPLC column provided the best separation of PFOS and PFHxS from interferent peaks. In addition to eliminating these interferences, the acetonitrile method has a shorter runtime and is more sensitive for most PFCs (limits of detection were 0.1 ng/mL except for PFOS (0.2 ng/mL)) than our previous method that used methanol for the HPLC separation. The present method should improve the precise and selective analysis of maternal and cord serum for PFCs. 相似文献
39.
Abstract The radiation-induced polymerization of glass-forming systems containing vinyl monomers was investigated. Irradiation below the secondorder transition temperature (Tg) of the systems causes no in-source polymerization but does cause a very rapid postpolymerization in the course of heating above Tg. Differential thermal analysis was carried out to estimate Tg and to follow the postpolymerization. 相似文献
40.