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101.
Takashima H Kawahara H Kitano M Shibata S Murakami H Tsukahara K 《The journal of physical chemistry. B》2008,112(48):15493-15502
The reconstituted zinc-myoglobin (ZnMb) dyads, ZnMb-[M(II)(edta)], have been prepared by incorporating a zinc-porphyrin (ZnP) cofactor modified with ethylenediaminetetraacetic acid (H(4)edta) into apo-Mb. In case of the monomeric ZnP(edta) cofactor coordinated by one pyridine molecule, ZnP(py)(edta), a spontaneous 1:1 complex with a transient metal ion was formed in an aqueous solvent, and the photoexcited singlet state of ZnP, (1)(ZnP)*, was quenched by the [Cu(II)(edta)] moiety through intramolecular photoinduced electron-transfer (ET) reaction. The rate constant for the intramolecular quenching ET (k(q)) at 25 degrees C was successfully obtained as k(q) = 5.1 x 10(9) s(-1). In the case of Co(2+), Ni(2+), and Mn(2+), intersystem crossing by paramagnetic effect was mainly considered between (1)(ZnP)* and the [M(II)(edta)] complex. For the ZnMb-[M(II)(edta)] systems, the intramolecular ET reaction between the excited singlet state of (1)(ZnMb)* and the [Cu(II)(edta)] moieties provided the slower quenching rate constant, k(q) = 2.1 x 10(8) s(-1), compared with that of the ZnP(py)(edta) one. Kinetic studies also presented the efficient fluorescence quenching of the (1)(ZnMb)*-[Co(II)(edta)] dyad. Our study clearly demonstrates that wrapping of the ZnP cofactor by the apoprotein matrix and synthetic manipulation at the Mb surface ensure metal ion-sensitive fluorescent dynamics of ZnMb and provides valuable information to elucidate the complicated mechanism of the biological photoinduced ET reactions of hemoproteins. 相似文献
102.
Stereoselective catalytic synthesis of 3-trifluoromethyl indolines through the [4+1] cycloaddition of benzoxazinones and sulfur ylides in a transition-metal-free manner was developed. In the presence of a catalytic amount of sodium hydride, aza-ortho-quinone methide intermediates were formed from trifluoromethyl benzoxazinones through decarboxylation after the first nucleophilic attack of sulfur ylides, which progressed to a second nucleophilic attack of sulfur ylides, resulting in the [4+1] cycloaddition. The key for this catalytic transformation is the dual attack of sulfur ylides on substrates. This unique transition-metal-free protocol is applicable to the synthesis of non-fluorinated vinyl-, ethynyl- or methyl-substituted indolines. The synthesis of 3-trifluoromethyl indoles was also achieved described under stoichiometric conditions. 相似文献
103.
[reaction: see text]. Rhodium complex-catalyzed carbonylative alkene-alkyne coupling proceeds using aldehydes as a CO source. Cinnamaldehyde is the best CO donor, and various cyclopentenones were provided in high isolated yields by a solvent-free system. 相似文献
104.
Morphological studies of a hydrogen-bonded LC polymer obtained by photopolymerization in LC solvents
Hideyuki Kihara Corresponding author Toshiaki Miura Ryoichi Kishi Takashi Yoshida Mitsuhiro Shibata Ryutoku Yosomiya 《Liquid crystals》2013,40(7):799-809
Anisotropic morphologies and the phase behaviour of a hydrogen-bonded LC polymer obtained by photopolymerization in two kinds of LC solvent are discussed. The hydrogen-bonded LC monomer, 4-(6-acryloyloxyhexyloxy) benzoic acid (A6OBA), was photopolymerized in 4-cyano-4′-hexyloxybiphenyl (6OCB) and in 4-cyano-4′-undecyloxybiphenyl (11OCB), which show a nematic phase and a smectic A phase, respectively. After photo-polymerization, the LC media were removed by extraction and the pure polymer was observed by scanning electron microscopy. SEM images showed that the polymer possessed fibrous morphology with a fibre diameter of a few micrometers, based on polymerization-induced phase separation. The overall geometries reflected typical LC characteristics such as schlieren and focal-conic fan textures. It was found that the hydrogen bond between benzoic acid groups in the monomer was rigid enough to fix the anisotropic phase-separated structure forming during the early stage of phase separation; however, it could not permanently maintain the fibre structure due to dissociation at elevated temperature. X-ray measurements revealed that a well developed layer structure of the hydrogen-bonded mesogen existed in the polymer obtained from the smectic phase of 11OCB, whereas a polymer layer structure could develop only partially from the nematic phase of 6OCB. 相似文献
105.
Shotaro Yoshida Kensuke Sumomozawa Kuniaki Nagamine Matsuhiko Nishizawa 《Macromolecular bioscience》2019,19(6)
A hydrogel‐based microchamber with organic electrodes for efficient electrical stimulations of human induced pluripotent stem cell‐derived cardiomyocytes (hiPSC‐CMs) is described. The microchamber is made from molecularly permeable, optically transparent, and electrically conductive polyvinyl alcohol (PVA) hydrogel and highly capacitive carbon electrode modified with poly(3,4‐ethylenedioxythiophene) (PEDOT). Spheroids of hiPSC‐CMs are cultured in microchambers, and electrically stimulated by the electrode for maturation. The large interfacial capacitance of the electrodes enables several days of electrical stimulation without generation of cytotoxic bubbles even when the electrodes are placed near the spheroids. The spheroids can be cultivated in the closed microchambers because of the permeated nutrients through the hydrogel, thus the spheroids are stably addressable and the culture medium around the sealed microchambers can be simply exchanged. Synchronized beating of the spheroids can be optically analyzed in situ, which makes it possible to selectively collect electrically responsive cells for further use. As the hydrogel is electrically conductive, the amount of electrical charge needed for maturing the spheroids can be reduced by configuring electrodes on the top and the bottom of the microchamber. The bioreactor will be useful for efficient production of matured hiPSC‐CMs for regenerative medicine and drug screening. 相似文献
106.
Nishiwaki N Konishi T Hirao S Yamashita Y Yoshikawa H Shimoda M 《Physical chemistry chemical physics : PCCP》2012,14(4):1424-1430
A novel use of GaAs, namely, as a scaffold for a heterogeneous palladium catalyst, is proposed. Hydroxy groups on the GaAs surface play important roles. During the adsorption of Pd(OAc)(2) on the GaAs surface, the hydroxy groups attract Pd(ii) species by anion exchange. A subsequent redox reaction proceeds to generate Pd(0) nanoparticles, which are stabilized on the GaAs surface. This process is confirmed by surface-sensitive measurements: diffuse reflection IR spectroscopy and X-ray photoelectron spectroscopy. Moreover, a more bulk-sensitive measurement, hard X-ray photoemission spectroscopy with synchrotron radiation, also supported our considerations. The amounts of Pd(0) nanoparticles on the surface were evaluated by catalytic activity, yield, and recyclability in the Heck reaction, in addition to the deposit test. 相似文献
107.
Shibata T Uchiyama T Yoshinami Y Takayasu S Tsuchikama K Endo K 《Chemical communications (Cambridge, England)》2012,48(9):1311-1313
Silahelicenes, which contain two silole moieties in a helically chiral structure, were synthesized by a chiral Ir-catalyzed intermolecular [2+2+2] cycloaddition of tetraynes with diynes along with a Ni-mediated intramolecular [2+2+2] cycloaddition. The photophysical properties of the obtained highly enantiomerically enriched silahelicenes (up to 93% ee) were also measured. 相似文献
108.
109.
High concentrations of arsenic were observed in the blubber of ringed seals (Pusa hispida) in our previous study. To better understand the arsenic accumulation in blubber of marine mammals, arsenicals in the blubber of ringed seal were characterized using high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC–ICPMS). The most predominant water-soluble arsenical in the blubber was dimethylarsinic acid (DMA), in spite of the predominance of arsenobetaine in other tissues. Lipid-soluble fraction was hydrolyzed under mild (tetraethylammonium hydroxide (TEAH) hydrolysis) and strong (NaOH hydrolysis) conditions, and then an aliquot of hydrolysate was injected onto HPLC–ICPMS. Both TEAH-labile and TEAH-stable/NaOH-labile lipid-soluble fractions contained precursors of DMA. These results suggest that the blubber might be the pool of DMA and DMA-containing precursors in ringed seals. 相似文献
110.
We have employed a cinchona alkaloid/Selectfluor-mediated enantioselective fluorination of the oxindole 2 to achieve the first enantioslective synthesis of BMS-204352 (MaxiPost, S-1), an effective opener of maxi-K channels. Fluorination occurred to produce S-1 with 84% ee using the bis-cinchona alkaloid (DHQ)(2)AQN. Recrystallization produced enantiomerically pure (>99% ee) product. Quinidine-mediated fluorination of 2 gave the (R)-antipode of 1 with 68% ee. 相似文献