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排序方式: 共有536条查询结果,搜索用时 31 毫秒
131.
A new method for the preparation of quaternary chiral aminals has been developed that employs an enamide‐type Overman rearrangement process. This methodology was applied to enantioselective total syntheses of (+)‐dibromophakellin and (+)‐dibromophakellstatin. 相似文献
132.
133.
134.
Using a competitive nitric oxide (NO)-trapping method between Fe–dithiocarbamate (DTC) complexes and liposome-encapsulated
2-[4-trimethylammonio]-4,4,5,5-tetramethyl-imidazoline-1-oxyl 3-oxide (TMAPTIO), NO-trapping rates of Fe–DTC complexes in
the presence of phosphatidylcholine liposomes were quantified for five kinds of Fe–DTC complexes. We investigated how the
DTC ligand structure influences the NO-trapping rates of Fe–DTC complexes. The negatively charged liposomes give a higher
NO-trapping rate of Fe–DTC complexes than do the positively charged ones, suggesting that the presence of a charge on the
liposome surface affects the NO-trapping rate processes of Fe–DTC complexes. In addition, on the basis of the pressure dependence
experiments for the competitive reaction, we evaluated the difference in activation volumes between the NO-trapping reactions
by Fe–DTC complexes and TMA-PTIO, which allowed us to consider possible reaction mechanisms for the NO-trapping processes. 相似文献
135.
Iwamoto S Kageshima H Yuasa T Nishioka M Someya T Arakawa Y Fukutani K Shimura T Kuroda K 《Optics letters》1999,24(5):321-323
Semi-insulating InGaAs/GaAs multiple quantum wells are fabricated by metal-organic vapor-phase epitaxy and proton implantation. Two-wave mixing gain and four-wave mixing diffraction efficiency are measured at wavelengths of 0.91-0.94microm in the Franz-Keldysh geometry. We observe a large photorefractive effect caused by the excitonic electro-optic effect. The maximum diffraction efficiency reaches ~1.5x10(-4) . 相似文献
136.
Sakamoto M Iwamoto T Nono N Ando M Arai W Mino T Fujita T 《The Journal of organic chemistry》2003,68(3):942-946
Asymmetric synthesis using frozen chirality generated by spontaneous crystallization was performed. Achiral asymmetrically substituted imide with a tetrahydronaphthyl group on the nitrogen atom crystallized in a chiral fashion, with space group P2(1)2(1)2(1). The molecular chirality generated by spontaneous crystallization was retained in cold THF. The half-life determined on the basis of decreasing optical activity followed by CD spectrometer was 7.8, 33.1, and 150.0 min at -20, -30, -40 degrees C, respectively. The energy barrier (DeltaG()) of racemization was calculated with the temperature dependence of the kinetic constant to be 18.24-18.36 kcal mol(-)(1) at 233-253 K. The memorized frozen chirality was transferred to permanent optically active alcohols by nucleophilic addition with n-buthyllithium. 相似文献
137.
Remarkable effect of pore size on the catalytic activity of mesoporous silica for the acetalization of cyclohexanone with methanol 总被引:2,自引:0,他引:2
Iwamoto M Tanaka Y Sawamura N Namba S 《Journal of the American Chemical Society》2003,125(43):13032-13033
The catalytic activity of mesoporous silica (MCM-41) for the acetalization of cyclohexanone shows a volcano-shaped dependence on the pore diameter. The diameter of the cyclohexanone molecule is ca. 0.75 nm, while its acetalization with methanol was well accelerated on MCM-41 with a pore diameter of approximately 1.9 nm, and smaller or larger pores were not suitable for the catalysis. The catalytic activity was independent of the Al concentration. 相似文献
138.
M. Tsuchiya Y. Iwamoto T. Masuzawa T. Shimizu T. Morita Y. Yanagihara 《Photochemistry and photobiology》1988,48(4):545-548
Abstract— Effects of active oxygen scavengers on cell inactivation and petite induction of yeast by the photodynamic action of euflavine were examined. Histidine, sodium azide, 1,3-diphenyl-isobenzofuran and p-carotene, which are singlet oxygen scavengers, inhibited photodynamic cell killing. Histidine and sodium azide inhibited petite induction, too. These results suggested that photobiological effects of euflavine are induced via singlet oxygen-mediated Type II reaction process. In this work, however, we found that ethanol, which is reported to be a hydroxyl radical scavenger, notably inhibited photodynamic cell inactivation and petite induction by euflavine. Inhibition of petite induction was increased with increasing concentration of ethanol. Decrease of absorbance of euflavine by irradiation was also inhibited by the addition of ethanol.
These results suggested that ethanol possibly acts as a singlet oxygen scavenger. 相似文献
These results suggested that ethanol possibly acts as a singlet oxygen scavenger. 相似文献
139.
T Masuzawa T Sekiguchi T Shimizu Y Iwamoto T Morita I Mifuchi Y Yanagihara 《Chemical & pharmaceutical bulletin》1989,37(2):414-417
Nine cell lines producing monoclonal antibodies (MAbs) against Leptospira interrogans serovar canicola strain Moulton were established by the cell fusion technique. The immunological reactivity of these MAbs with various kinds of serogroups, serovars and strains were examined by microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA). MAbs W1-W3 derived from mice, which were immunized with whole cells of the strain Moulton, reacted with the serogroups Canicola, Icterohaemorrhagiae and Pyrogenes. On the other hand, MAbs A1-A6 derived from mice immunized with the outer envelope (OE) fraction, which showed a potent protective activity and was extracted with ammonium hydroxide from the strain Moulton, reacted specifically with the serogroup Canicola alone in MAT. A difference in antigenic structure between subserogroup A (canicola subgroup) and subserogroups B (schüeffneri subgroup) of the serogroup Canicola was demonstrated by MAT using the MAbs. All the MAbs clearly agglutinated serovars of subserogroup A except for serovars kamituga, jonsis and bindjei, but did not react with any serovars of subserogroup B. These findings suggest that MAb highly specific to each serovar is readily available by OE immunization and is useful for the classification of Leptospira. 相似文献
140.
The enzymatic activities of horseradish peroxidase solubilized in reversed micelles of bis(2-ethylhexyl)sodium sulfosuccinate formed in octane at various
o values (
o=[H2O]/[AOT]) were investigated by studying the catalytic oxidation of hydroquinone and p-cresol. These enzymatic reactions obeyed Michaelis-Menten kinetics. The turnover number of the enzymatic reaction of hydroquinone solubilized in the water pool increased with a decrease in
o value. On the other hand, the dependence of the turnover number of the enzymatic reaction of p-cresol solubilized in octane on the
o value was similar to that in the case of hydroquinone, although even at higher
o values the turnover number was smaller than that in water. Furthermore, it was suggested by spectrophotometric and circular dichroism measurements that the conformational change of enzyme induced the change in enzymatic activity. 相似文献