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71.
Ikeda S Sanuki R Miyachi H Miyashita H Taniguchi M Odashima K 《Journal of the American Chemical Society》2004,126(33):10331-10338
A Ni(0)/ZnCl(2) system effectively promotes the coupling of enones and alkene-tethered alkynes. In the reaction with 1,6-enynes, the oxidative cyclization of Ni(0) species on enones across the alkyne part followed by ZnCl(2)-promoted cleavage generates alkenylnickel intermediates. Subsequent migratory insertion of the tethered alkene occurs with 5-exo-cyclization. When the resulting sigma-alkylnickel intermediates have beta-hydrogen atoms, the reaction terminates by beta-hydrogen elimination to provide cyclopentane derivatives. On the other hand, a sigma-alkylnickel intermediate that does not have beta-hydrogen atoms undergoes the insertion of a second alkene unit to cause a domino effect via a three-fold C-C bond formation process with and without the cleavage of one C-C bond. 相似文献
72.
Polyion complex micelles entrapping enzyme molecules in the core provide a unique reaction field inducing a remarkable elevation of enzymatic reactivity through a drastic change in the binding specificity between the enzyme and substrate. On-off switching of this enhanced effect was achieved through the destabilization of the core domain by applying a pulse electric field. 相似文献
73.
Sugiyasu K Fujita N Takeuchi M Yamada S Shinkai S 《Organic & biomolecular chemistry》2003,1(5):895-899
A 1,10-phenanthroline-appended cholesterol-based gelator (1) and its nongelling reference compound (2) were synthesized. Among 19 solvents tested herein, gelator 1 could gelate 11 solvents including alcohols, dipolar aprotic solvents, organic acids and a base (triethylamine), indicating that 1 acts as a versatile gelator. The TEM observation gave a visual image showing that fibrillar aggregates are entangled in the three-dimensional network structure. In the fluorescence measurements, most gels afforded an emission maximum at 394 nm (purple emission), whereas only the acetic acid gel afforded an emission maximum at 522 nm (yellow emission). Thus, the influence of protonation of the 1,10-phenanthroline nitrogens (by trifluoroacetic acid) on the fluorescence properties in the gel phase was investigated in detail. The results have established that the fluorescence intensity of 1 x H+ becomes particularly strong in the gel phase, presumably because of the energy transfer from neutral 1* to protonated 1 x H+ and the restriction of the 1 x H+ molecular motion. The finding suggests the possibility that the gel system would be useful not only as a new proton-sensitive fluorescence system but also as a new medium for designing efficient energy transfer systems. 相似文献
74.
Kazunori Kodaka Hiroyuki Osaka 《Proceedings of the American Mathematical Society》2001,129(4):999-1003
A -algebra is said to have the FS-property if the set of all self-adjoint elements in has a dense subset of elements with finite spectrum. We shall show that this property is not stable under taking the minimal -tensor products even in case of separable nuclear -algebras.
75.
Abstract Accuracy of hydrostatic pressure measurement in a diamond-anvil cell (DAC) depends on the reproducibility of ruby RI fluorescent measurement. The larger scatter in R, fluorescent wavelength shift than the reproducibility of spectroscopic measurement was observed among appropriately mirror-finished ruby plates before setting up in DAC. The characteristics of the scatter changed after loading DAC up to pressure over hydrostatic limit. They vanished by annealing the ruby plates. These phenomena are presumably due to the appearance and disappearance of the residual stress in the ruby crystal. Such hysteresis of ruby fluorescent wavelength shift by pressure and its annealing effect are discussed. 相似文献
76.
Shin-ichi Nakakita Kayo Hasehira Tomohiro Hosokawa Masaaki Tokuda Ken Izumori Kaoru Takegawa Jun Hirabayashi 《Journal of chromatography. A》2009,1216(26):5112-5115
A rare sugar is considered to be a monosaccharide rarely found in nature. To investigate their natural distribution and biological roles, a robust analytical system must be used to isolate, identify, and quantify them. Herein, we report the development of such a system that can specifically quantify and chromatographically separate four aldopentoses and eight aldohexoses tagged with 2-aminopyridine. Purified monosaccharides derivatized with a pyridylamino moiety (PA–monosaccharides) are first chromatographed over a high-performance anion-exchange resin. But, because two of the PA–aldohexoses used in this study, PA–talose and PA–idose, co-elute with the common saccharides, PA–glucose and PA–mannose, respectively, a second chromatographic step, reversed-phase high-performance liquid chromatography, is used to completely separate them. Thus, as shown by the results of this study, chromatographic separation of PA–monosaccharides is achievable and provides a quantitative measurement of common and rare isomeric aldopentoses and aldohexoses. 相似文献
77.
78.
Kazunori Nakano Kazuaki Aburaya Ichiro Hisaki Norimitsu Tohnai Mikiji Miyata 《Chemical record (New York, N.Y.)》2009,9(2):124-135
We have systematically investigated structures and properties of inclusion crystals of bile acids and their derivatives. These steroidal compounds form diverse host frameworks having zero‐, one‐ and two‐dimensional cavities, causing various inclusion behaviors towards many organic compounds. The diverse host frameworks exhibit the following guest‐dependent flexibility. First, the frameworks mainly depend on the included guests in size and shape. The size‐dependence is quantitatively estimated by the parameter PCcavity, which is the volume ratio of a guest molecule to a host cavity. The resulting values of PCcavity lie in the range of 42–76%. Second, each of the host frameworks has its own range of the values. Some guests can employ two different frameworks with the boundary values, explaining formation of polymorphic crystals. Third, the host frameworks are selected by host–guest interactions through weak hydrogen bonds, such as NH/π and CH/O. The weak hydrogen bonds play an important role for various selective inclusion processes. Fourth, the host frameworks are dynamically exchangeable, resulting in intercalation and polymerization in the cavities. These static and dynamic structures of the frameworks demonstrate great potential of crystalline organic inclusion compounds as functional materials. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 124–135; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20171 相似文献
79.
Yoko Masuda Kozue Hirabayashi Keiko Sakuma Tadashi Nakanishi 《Colloid and polymer science》2002,280(5):490-494
The swelling behavior of poly(ethylene oxide) (PEO) gels in aqueous solutions of sodium dodecyl sulfate (SDS) with and without
NaCl was investigated. In the absence of NaCl, PEO gels with different degrees of cross-linking began to swell from a concentration
lower than the critical micelle concentration (cmc) of SDS, then showed sigmoidal enhancements of swelling in a higher SDS
concentration region until the degrees of swelling reached maximum values. The SDS concentration at which the swelling began
to appear was in reasonable agreement with the critical aggregation concentration (cac) value reported for the aqueous PEO
system. For the cases where NaCl was present, the swelling behavior of PEO gel was different from that when NaCl was absent
in the following way. The concentrations where the swelling begins to appear, and hence those where the degree of swelling
rises steeply, decreased with an increase in NaCl concentration. The ultimate degrees of swelling at higher concentration
regions also decreased with an increase in the NaCl concentration. The lowering of the SDS concentrations at which the PEO
gel began to swell is in line with the decreases in the cmc of SDS solutions containing NaCl and also with the decreases in
the cac of PEO solution.
Electronic Publication 相似文献
80.
Kazunori Ishikawa Yoko Nambu Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》1989,27(5):1625-1629
Polypeptide membranes with several lengths of spacers [? (CH2)n? ; n = 3, 6, 12] between the polymer matrix and viologen moiety as a functional group were prepared. Reduction of K3Fe(CN)6 with Na2S2O4 across the obtained membrane in aqueous media were carried out and reduction rate of K3Fe(CN)6 across the membrane of n = 6 was faster than that of n = 3. However, the reduction of the membrane (n = 12) did not proceed chemically and electrochemically at all. 相似文献