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排序方式: 共有308条查询结果,搜索用时 322 毫秒
301.
Hidehiko Nakano Masahiro Nishioka Osamu Sangen Yoshitake Yamamoto 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2919-2928
The effect of quaternized poly(4-vinyl pyridine)(QPVP) on the α,β-elimination of series catalyzed to pyridoxall (PL) or pyridoxal phosphate (PLP) and metla ions was investigated. In PLP-Al3+ and PLP-Fe3+ systems QPVP showed simulation of about forefold; this stimulation was reduced in the presence of 0.5 M KCI. The catalytic activities of PL-Al3+ and PL-Fe3+ were lower compared to the corresponding PLP systems; stimulation by QPVP was also seen, through the extent of stimulation was smaller. The contribution of the electrostatic force between the polymer and the metal complex of the Schiff base was suggested to account for the stimulation. The pyridine moiety on the partialy quaternized PVP did not seen toparticpate in the catalysis. In PLP-Cu2+, PL-Cu2+, and PLP-VO2+ systems, however, QPVP showed marked inhibition. This inhibition by QPVP was also mitigated in the presence of 0.5 M KCl. 相似文献
302.
Feifel R Tanaka T Kitajima M Tanaka H De Fanis A Sankari R Karlsson L Sorensen S Piancastelli MN Prümper G Hergenhahn U Ueda K 《The Journal of chemical physics》2007,126(17):174304
The valence character of O 1s-->Rydberg excited O2 is investigated by means of participator Auger decay spectroscopy, performed at selected photon energies across the K-shell resonance region, and by means of partial ion yield x-ray absorption spectroscopy. For several of the excitation energies studied, the authors find substantial sigma*(4Sigmau-, 2Sigmau-) valence character being mixed with nssigma and npsigma (4Sigmau-, 2Sigmau-) Rydberg states. An experimental indication of a coupling between the channels associated with quartet and doublet ion cores is considered and discussed. New spectroscopic constants are derived for the singly ionized X 2Pig state of O2 based on the observation of at least 20 vibrational sublevels. 相似文献
303.
Peroxynitrite generation from a NO-releasing nitrobenzene derivative in response to photoirradiation
Ieda N Nakagawa H Horinouchi T Peng T Yang D Tsumoto H Suzuki T Fukuhara K Miyata N 《Chemical communications (Cambridge, England)》2011,47(22):6449-6451
Photocontrollable ONOO(-) generation from a nitrobenzene derivative was demonstrated. The designed compound released NO in response to photoirradiation, and the resulting semiquinone reduced molecular oxygen to generate O(2)˙(-); reaction of the two generated ONOO(-), as confirmed with an ONOO(-) fluorescent probe, HKGreen-3. 相似文献
304.
Ogoshi T Aoki T Kitajima K Fujinami S Yamagishi TA Nakamoto Y 《The Journal of organic chemistry》2011,76(1):328-331
We monitored the progress of formation of dimethoxypillar[5]arene by size-exclusion chromatography. Surprisingly, the cyclization reaction completely finished in just 3 min. By improving the reaction conditions and purification process, we successfully obtained dimethoxypillar[5]arene in a short time and in high yield (71%) from commercially available reagents. By improving the deprotection reaction of the methoxy moieties, pillar[5]arene was isolated quantitatively. Single crystal X-ray analysis confirmed the structure of pillar[5]arene in the solid state. 相似文献
305.
Naoki Nanashima Kayo Horie Maiko Kitajima Shizuka Takamagi Kasumi Mikami Naoya In Toshiko Tomisawa 《Molecules (Basel, Switzerland)》2021,26(13)
Blackcurrant extract (BCE) ameliorates dyslipidemia in menopausal model animals and in elderly women at a risk of dyslipidemia. However, it is unknown whether the daily intake of BCE can prevent lipid abnormalities in healthy individuals. Lipids are essential for the body, but they also cause arteriosclerosis. In this noncomparative pilot study, we examined the effects of BCE administered for 29 days on serum lipids in young healthy women. Blood samples were collected before and on days 4 and 29 after BCE intake, and 20 lipoprotein fractions in the serum were separated using a gel-permeation high-performance liquid chromatography method to measure the triacylglycerol and cholesterol levels in lipoproteins. There were no effects on lipids on day 4 of BCE intake, but the total cholesterol level decreased on day 29. Furthermore, the levels of total very-low-density lipoprotein (VLDL) cholesterol, small VLDL cholesterol, and large low-density lipoprotein cholesterol were significantly decreased. These results suggest that the daily intake of BCE has a hypocholesterolemic effect in healthy women, and that it is effective in preventing atherosclerosis. 相似文献
306.
Tsuneyuki Sato Takashi Kitajima Makiko Seno 《Journal of polymer science. Part A, Polymer chemistry》1997,35(10):1891-1900
The polymerization of benzyl N-(2,6-dimethylphenyl)itaconamate (BDMPI) with benzoyl peroxide (BPO) in N,N-dimethylformamide (DMF) was studied kinetically by ESR. The polymerization rate (Rp) at 70°C was given by Rp = k[BPO]0.78[BDMPI]1.1. The overall activation energy of polymerization was determined to be 83.7 kJ/mol. The number-average molecular weight of poly(BDMPI) was in the range of 1500–2000 by gel permeation chromatography. From the ESR study, the polymerization system was found to involve ESR-observable propagating radicals of BDMPI under practical polymerization conditions. Using the polymer radical concentration by ESR, the rate constants of propagation (kp) and termination (kt) were determined in the temperature range of 50–70°C. The kp value seemed dependent on the chain-length of propagating radical. The analysis of polymers by the MALDI-TOF mass spectrometry suggested that most of the resulting polymers contain the dimethylamino terminal group. The copolymerization of BDMPI (M1) and styrene (M2) at 50°C in DMF gave the following copolymerization parameters; r1 = 0.49, r2 = 0.26, Q1 = 1.2, and e1 = +0.63. The thermal behavior of poly(BDMPI) was examined by dynamic thermogravimetry and differential scanning calorimetry. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1891–1900, 1997 相似文献
307.
308.
Naoya Ieda Masato Sawada Runa Oguchi Masato Itoh Seina Hirakata Daisuke Saitoh Akito Nakao Mitsuyasu Kawaguchi Prof. Kazunobu Sawamoto Prof. Toshitada Yoshihara Prof. Yasuo Mori Prof. Hidehiko Nakagawa 《Angewandte Chemie (International ed. in English)》2023,62(20):e202217585
We present an optochemical O2 scavenging system that enables precise spatiotemporal control of the level of hypoxia in living cells simply by adjusting the light intensity in the illuminated region. The system employs rhodamine containing a selenium or tellurium atom as an optochemical oxygen scavenger that rapidly consumes O2 by photochemical reaction with glutathione as a coreductant upon visible light irradiation (560–590 nm) and has a rapid response time, within a few minutes. The glutathione-consuming quantum yields of the system were calculated as about 5 %. The spatiotemporal O2 consuming in cultured cells was visualized with a hypoxia-responsive fluorescence probe, MAR. Phosphorescence lifetime imaging was applied to confirmed that different light intensities could generate different levels of hypoxia. To illustrate the potential utility of this system for hypoxia research, we show that it can spatiotemporally control calcium ion (Ca2+) influx into HEK293T cells expressing the hypoxia-responsive Ca2+ channel TRPA1. 相似文献