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101.
Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) 总被引:1,自引:0,他引:1
Lin M Katsumura Y Hata K Muroya Y Nakagawa K 《Journal of photochemistry and photobiology. B, Biology》2007,89(1):36-43
The reactions between edaravone and various one-electron oxidants such as (*)OH, N(3)(*), Br(2)(-), and SO(4)(-), have been studied by pulse radiolysis techniques. The transient species produced by the reaction of edaravone with (*)OH radical shows an absorption band with lambda(max)=320 nm, while the oxidation by N(3)(*), Br(2)(-), SO(4)(-) and CCl(3)OO(*) results in an absorption band with lambda(max)=345 nm. Different from the previous reports, the main transient species by the reaction of edaravone with (*)OH radical in the absence of O(2) is attributed to OH-adducts. At neutral condition (pH 7), the rate constants of edaravone reacting with (*)OH, N(3)(*), SO(4)(-), CCl(3)OO(*), and e(aq)(-) are estimated to be 8.5x10(9), 5.8x10(9), 6x10(8), 5.0x10(8) and 2.4x10(9)dm(3)mol(-1)s(-1), respectively. From the pH dependence on the formation of electron adducts and on the rate constant of edaravone with hydrated electron, the pK(a) of edaravone is estimated to be 6.9+/-0.1. 相似文献
102.
Oseki Y Fujitsuka M Sakamoto M Majima T 《The journal of physical chemistry. A》2007,111(39):9781-9788
We studied the energy transfer processes in the molecular array consisting of pyrene (Py), biphenyl (Ph2), and bisphthalimidethiophene (ImT), (Py-Ph2)2-ImT, during two-color two-laser flash photolysis (2-LFP). The first laser irradiation predominantly generates ImT in the lowest triplet excited state (ImT(T1)) because of the efficient singlet energy transfer from Py in the lowest singlet excited state to ImT and, then, intersystem crossing of ImT. ImT(T1) was excited to the higher triplet excited state (Tn) with the second laser irradiation. Then, the triplet energy was rapidly transferred to Py via a two-step triplet energy transfer (TET) process through Ph2. The efficient generation of Py(T1) was suggested from the nanosecond-picosecond 2-LFP. The back-TET from Py(T1) to ImT was observed for several tens of microseconds after the second laser irradiation. The estimated intramolecular TET rate from Py(T1) to ImT was as slow as 3.1 x 104 s-1. Hence, long-lived Py(T1) was selectively and efficiently produced during the 2-LFP. 相似文献
103.
Shinoda K Hasegawa T Sato H Shinozaki M Kuramoto H Takamiya Y Sato T Nikaidou N Watanabe T Hoshino T 《Chemical communications (Cambridge, England)》2007,(40):4140-4142
A biosynthetic intermediate of violacein produced by the mixed enzymes of VioABDE was elucidated to be 5-(5-hydroxy-1H-indol-3-yl)-3-(1H-indol-3-yl)-1H-pyrrole-2-carboxylic acid, named protoviolaceinic acid, indicating that VioC, responsible for the final biosynthetic step, works to oxygenate at the 2-position of the right side indole ring, and that the oxygenation reaction to form the central pyrrolidone core proceeds in a non-enzymatic fashion. 相似文献
104.
Keiko Ohkura Hidekazu Nishizawa Takashi Obi Akira Hasegawa Masahiro Yamaguchi Nagaaki Ohyama 《Optical Review》2000,7(3):193-198
In the analysis of a medical image database aimed at formulating useful knowledge for image diagnosis requires an unsupervised image processing technique without preconceived knowledge. In this paper, we propose a method for unsupervised image segmentation, which is suitable for finding the features contained in an image. A small region around each pixel is considered as a pattern vector, and the set of pattern vectors acquired from the whole image is classified using the hierarchical clustering technique. In hierarchical clustering, the classification of pattern vectors is divided into two clusters at each node according to the statistical criterion based on the entropy in thermodynamics. Results of the test image generated by the Markov random field (MRF) model and real medical images photomicrographs of a colon tumor are shown. 相似文献
105.
Daisuke Taura Yosuke Taniguchi Akihito Hashidzume Akira Harada 《Macromolecular rapid communications》2009,30(20):1741-1744
Interaction of β‐cyclodextrin (β‐CD) with alternating copolymers (pAdMA and pAdPhMA) of sodium maleate with adamantyl (Ad) and with adamantylphenyl (AdPh) vinyl ether has been investigated by several NMR techniques. Comparing the apparent association constants (K) for the polymers with the K for the model compounds, which are determined by the analysis of 1H NMR and isothermal titration calorimetry data, respectively, the selectivities of β‐CD toward Ad and AdPh moieties are contrasting for the model and polymer systems. This phenomenon is described by circular dichroism and 2D NMR as follows; the most stable inclusion complex for the β‐CD/AdPh model system is extremely destabilized for the corresponding polymer system because of competition with hydrophobic interaction between neighboring AdPh moieties.
106.
Toshihiro Isobe Yosuke Nakano Yoshikazu Kameshima Akira Nakajima Kiyoshi Okada 《Applied Surface Science》2009,255(20):8710-8713
The repulsive force originating from steric hindrance of polymers in aqueous solvent was investigated using scanning probe microscopy (SPM). The contact angle (CA) of ammonium poly(acrylic acid) (PAA) solution on the Si surface was measured to estimate the state of the Si substrate. Results of CA measurement show that the Si surface was fully covered with PAA at 0.1 mass% in aqueous solution. The interaction force between the Si tip and the wafer was estimated using the SPM force curve mode. The force curve measured in the ion-exchanged purified water showed the typical relation predicted by Derjaguin-Landau-Verway-Overbeek (DLVO) theory. However, the force curve shape in the 0.1 mass% PAA solution was significantly different. Only a repulsive force was observed at less than about 4 nm of separation distance between the Si wafer and cantilever tip. This distance originated from the steric repulsions of PAA adsorbed onto the Si wafer and cantilever tip. 相似文献
107.
The static and dynamical local spin susceptibility of the nonstoichiometric organic conductor, κ-(BEDT-TTF)4Hg2.78Cl8, is studied by 13C NMR spectroscopy from room temperature down to 1.7 K. We observe a gradual growth of inhomogeneity in the spin state as a spectral broadening down to the lowest temperature, which is sustained even under 0.4 GPa but suppressed under 0.8 GPa. The emergence of the inhomogeneity is discussed in the light of the doped triangular-lattice Mott insulator. 相似文献
108.
An unstable intermediate proepitheaflagallin B (2), a precursor of proepitheaflagallin (3), was isolated as an enzymatic oxidation product of (−)-epigallocatechin (1), and the structure of 2 was determined based on spectroscopic data. The structure and its decomposition revealed that the detailed production mechanism of proepitheaflagallin (3) via a bicyclo[3.2.1]octane-type intermediate was related to that of major black tea pigments, theaflavins. 相似文献
109.
Mitsumasa Taguchi Grard Baldacchino Satoshi Kurashima Atsushi Kimura Yumi Sugo Yosuke Katsumura Koichi Hirota 《Radiation Physics and Chemistry》2009,78(12):1169-1174
This article reports a highly sensitive transient absorbance measurement system using pulsed energetic ions. The ions were pulsed by a beam chopper, which was synchronized with the cyclotron, and accelerated to the desired energy around 18 MeV/u. H, He, C and Ne ions can be used for the transient absorption measurement. The optical system can measure an absorbance smaller than 1.0×10−4 in the wavelength range of 400–740 nm. 相似文献
110.
Natsumi Tanaka Takahiro Suzuki Dr. Takehiko Matsumura Yosuke Hosoya Masahisa Nakada Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(14):2580-2583
Intelligent design : The total synthesis of the cytotoxic (?)‐FR182877 relies on 1) tandem Diels–Alder reactions to close rings A–D (see scheme), 2) a palladium‐mediated 7‐exo‐trig reaction, and 3) an iridium‐mediated isomerization followed by epimerization and stereoselective reduction.