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51.
52.
Kano N Komatsu F Yamamura M Kawashima T 《Journal of the American Chemical Society》2006,128(21):7097-7109
Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by (1)H, (13)C, (19)F, and (29)Si NMR spectra, UV-vis spectra, and X-ray crystallographic analyses. In the UV-vis spectra, silyl groups caused red shifts of both the n-pi and pi-pi transitions of the azo group compared with the transitions of the unsubstituted azobenzene. The E-isomers of the fluorosilanes showed an intramolecular interaction between a nitrogen atom of the azo group and the silicon atom, leading their intermediate structures between a distorted trigonal bipyramidal structure and a tetrahedral structure around the silicon atoms, which were revealed by the X-ray crystallographic analyses and the NMR spectra. On the other hand, silanes without fluorine atoms showed tetrahedral structures in the absence of such an interaction. The photoirradiation of the E-isomers of the fluorosilanes afforded reversibly the corresponding Z-isomers in good yields. The silicon atoms of the Z-isomers were found to be tetracoordinate in the absence of Si-N interactions by the (29)Si NMR spectra. The coordination numbers of the silicon atom of the fluorosilanes were reversibly switched between four and five by photoirradiation. These properties were compared to those of a tetrafluoro[2-(phenylazo)phenyl]silicate. 相似文献
53.
Bunichiro Yamada Fuminori Oku Takahiro Harada 《Journal of polymer science. Part A, Polymer chemistry》2003,41(5):645-654
The addition of propagating radicals of methyl acrylate (MA) and styrene (St) to CH2?C(CO2CH3)CH2? and CH2?C(C6H5)CH2? ω‐end groups of poly(methyl methacrylate) (PMMA) and polystyrene (PSt) was investigated. The end groups were as reactive as MA and St toward the poly(methyl acrylate) (PMA) and PSt radicals, respectively. The adduct radical derived from the two types of PMMA end groups and PMA radicals underwent β fragmentation exclusively to yield PMMA radicals and end groups bound to PMA chains. The addition of PSt radicals to PMMA with CH2?C(CO2Me)CH2? end groups resulted in adduct radicals that underwent β fragmentation and addition to St or coupling with PSt radicals. Adduct radicals formed by the addition of PMA radicals to both types of end groups of PSt exclusively formed C? C bond by coupling with PMA radicals to form branched structures or by addition to MA monomer to give a copolymer. The fate of the adduct radicals was highly dependent on the type of polymer chain and the substituent bound to the end group. Steric congestion of the adduct radical arising from the α‐methyl group of the PMMA chain was considered to be crucial for fragmentation to expel the PMMA radical. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 645–654, 2003 相似文献
54.
Fuminori Yamaguchi Sho Yamamura Seiko Shimamoto Hiroshi Tokumitsu Masaaki Tokuda Ryoji Kobayashi 《Applied biochemistry and biotechnology》2014,172(1):237-247
Suramin is an activator of ryanodine receptors and competitively binds to the calmodulin-binding site. In addition, S100A1 and calmodulin compete for the same binding site on ryanodine receptors. We therefore studied the effects of suramin on protein phosphatase 5 (PP5) and S100-activated PP5. In the absence of S100 proteins, suramin bound to the tetratricopeptide repeat (TPR) domain of PP5 and activated the enzyme in a dose-dependent manner. In the presence of S100A2/Ca2+, lower concentrations of suramin dose-dependently inhibited PP5 activity as an S100 antagonist, whereas higher concentrations of suramin reactivated PP5. Although the C-terminal fragment of heat shock protein 90 (HspC90) also weakly activated PP5, the binding site of suramin and HspC90 may be different, and addition of suramin showed no clear effect on the phosphatase activity of PP5. Similar biphasic effects of suramin were observed with S100A1-, S100B- or S100P-activated PP5. However, the inhibitory effects of lower concentrations of suramin on S100A6-activated PP5 are weak and high concentrations of suramin further activated PP5. SPR and the cross-linking study showed inhibition of the interaction between S100 protein and PP5 by suramin. Our results revealed that suramin is a novel PP5 activator and modulates S100-activated PP5 activity by competitively binding to the TPR domain. 相似文献
55.
Hirokazu Hirano Noritaka Masaki Takahiro Hayasaka Yoshiko Watanabe Kazuma Masumoto Tetsuji Nagata Fuminori Katou Mitsutoshi Setou 《Analytical and bioanalytical chemistry》2014,406(5):1355-1363
Periodontal disease is a serious dental problem because it does not heal naturally and leads to tooth loss. In periodontal disease, inflammation at periodontal tissue is thought as predominant, and its effect against tooth itself remains unclear. In this study, we applied matrix-assisted laser desorption/ionization imaging mass spectrometry (IMS) to teeth for the first time. By comparing anatomical structure of tooth affected with periodontal disease with normal ones, we analyzed traces of the disease on tooth. We found signals characteristic of enamel, dentin, and dental pulp, respectively, in mass spectra obtained from normal teeth. Ion images reconstructed using these signals showed anatomical structures of the tooth clearly. Next, we performed IMS upon teeth of periodontal disease. Overall characteristic of the mass spectrum appeared similar to normal ones. However, ion images reconstructed using signals from the tooth of periodontal disease revealed loss of periodontal ligament visualized together with dental pulp in normal teeth. Moreover, ion image clearly depicted an accumulation of signal at m/z 496.3 at root surface. Such an accumulation that cannot be examined only from mass spectrum was revealed by utilization of IMS. Recent studies about inflammation revealed that the signal at m/z 496.3 reflects lyso-phosphatidylcholine (LPC). Infiltration of the signal is statistically significant, and its intensity profile exhibited the influence has reached deeply into the tooth. This suggests that influence of periodontal disease is not only inflammation of periodontal tissue but also infiltration of LPC to root surface, and therefore, anti-inflammatory treatment is required besides conventional treatments. 相似文献
56.
57.
Optical Review - In hyperspectral imaging, the captured signal is often affected by saturation due to specular reflection or a peaky spectrum. In this paper, we propose a restoration method for... 相似文献
58.
Fuminori Hyodo Shingo Matsumoto Nallathamby Devasahayam Christopher Dharmaraj Sankaran Subramanian James B. Mitchell Murali C. Krishna 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,197(2):181-185
Nitroxides, unlike trityl radicals, have shorter T2s which until now were not detectable in vivo by a time-domain pulsed Electron Paramagnetic Resonance (EPR) spectrometer at 300 MHz since their phase memory times were shorter than the spectrometer recovery times. In the current version of the time-domain EPR spectrometer with improved spectrometer recovery times, the feasibility of detecting signals from nitroxide radicals was tested. Among the nitroxides evaluated, deuterated 15N-Tempone (15N-PDT) was found to have the longest T2. The signal intensity profile as a function of concentration of these agents was evaluated and a biphasic behavior was observed; beyond a nitroxide concentration of 1.5 mM, signal intensity was found to decrease as a result of self-broadening. Imaging experiments were carried out with 15N-PDT in solutions equilibrated with 0%, 5%, 10%, and 21% oxygen using the single point imaging (SPI) modality in EPR. The image intensity in these tubes was found to depend on the oxygen concentration which in turn influences the T2 of 15N-PDT. In vivo experiments were demonstrated with 15N-PDT in anesthetized mice where the distribution and metabolism of 15N-PDT could be monitored. This study, for the first time shows the capability to image a cell-permeable nitroxide in mice using pulsed EPR in the SPI modality. 相似文献
59.
Structures of Stoichiometric Sodium Oxide Cluster Cations Studied by Ion Mobility Mass Spectrometry
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Motoyoshi Nakano Yudai Ishimura Riki Hotta Daiki Hebiguchi Toshiaki Nagata Fuminori Misaizu 《化学物理学报(中文版)》2019,32(2):193-199
Structures of stable compositions of sodium oxide cluster cations (NanOm+,n≤11) have been investigated by ion mobility mass spectrometry. Stoichiometric compositions series, Na(Na2O)(n-1)/2+ (n=3, 5, 7, 9, and 11), were observed as stable composition series, and NaO(Na2O)(n-1)/2+ series (n=5, 7, 9, and 11) were observed as secondary stable series in the mass spectra. To assign the structures of these cluster ion series, collision cross sections between the ions and helium buffer gas were determined experimentally from the ion mobility measurements. Theoretical collision cross sections were also calculated for optimized structures of these compositions. Finally, the structures of Na(Na2O)(n-1)/2+ and NaO(Na2O)(n-1)/2+ were assigned to those having similar structural frames for each n except for n=9. All bonds in the assigned structures of Na(Na2O)(n-1)/2+ were between sodium and oxygen. On the other hand, there was one O-O bond in addition to Na-O bonds in NaO(Na2O)(n-1)/2+. This result indicates that NaO(Na2O)(n-1)/2+ have a peroxide ion (O22-) as a substitute for an oxide ion (O2-) of Na(Na2O)(n-1)/2+. As a result, both stable series, Na(Na2O)(n-1)/2+ and NaO(Na2O)(n-1)/2+, are closed-shell compositions. These closed-shell characteristics have a strong influence on the stability of sodium oxide cluster cations. 相似文献
60.
K. Ohshimo F. Misaizu K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):339-342
Cluster anions of a sodium atom with acrylonitrile
molecules,
(n = 0–6), have been studied by
negative-ion photoelectron spectroscopy. In addition,
theoretical calculations by using density functional theory have
been performed to obtain optimized structures and vertical
detachment energies. For Na(AN)–, the
spectrum can be explained by excitation of two different isomers
of the anion. For
, a broad band is found in the
photoelectron spectrum, whose profile is almost identical with
those of previously reported photoelectron spectra of
and a negative ion of chemically
synthesized 1,3,5-cyclohexanetricarbonitrile (CHTCN) molecule.
From this resemblance of band profiles, we conclude that
oligomerization of (AN)3 takes place in
and the CHTCN is formed as the
intracluster reaction product. 相似文献