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1.
Masaki Takeguchi Kazutaka Mitsuishi Miyoko Tanaka Kazuo Furuya 《Microscopy and microanalysis》2004,10(1):134-138
About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described. 相似文献
2.
[reaction: see text] Ethyl 1-thio-2,3,4,6-tetrakis-O-triisopropylsilyl-beta-d-glucopyranoside, ethyl 6-O-benzyl-1-thio-2,3,4-tris-O-triisopropylsilyl-beta-d-glucopyranoside, and ethyl 6-O-pivaloyl-1-thio-2,3,4-tris-O-triisopropylsilyl-beta-d-glucopyranoside induced highly beta-selective O-glucosidations. Among them, the 6-O-pivaloylated substrate provided the best selectivity up to alpha/beta = 3:97 with cyclohexylmethanol, and the substrate was used for glucosidations with secondary and tertiary alcohols in a highly beta-selective manner. The selectivity would be caused by the twist-boat conformation of the pyranose; this is the first beta-selective O-glucosidation based on conformational control of the pyranose ring. 相似文献
3.
Watanabe S Sonobe M Arai M Tazume Y Matsuo T Nakamura T Yoshida K 《Chemical communications (Cambridge, England)》2002,(23):2866-2867
A gold nanoparticle surface-modified with amide ligands shows enhanced optical sensing of anions: the detection limit is increased by about three orders of magnitude higher than that originally expected from the anion binding ability of neutral amide ligands. 相似文献
4.
5.
Miyoko Suzuki Yoshio Sasaki József Szejtli Éva Fenyvesi 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(4):459-468
Low molecular mass fractions of water soluble -, -, and -cyclodextrin epichlorohydrin polymer products (cdx-Ep) were characterized by13C nuclear magnetic resonance. The derivatives proved not to be polymers, but substituted cdx having one or two glyceryl groups per one glucose at the C-2, C-3 and C-6 positions. Spectra of analogous hydroxy-propyl -cdx indicate that the degree of substitution is rather higher at the C-6 position. Methyl orange (MO) was included into nine kinds of cdx having different inner diameters and hydrophobic torus heights; -, -, and -cdx monomers, 2, 6-dimethyl and 2, 3, 6-trimethyl -cdx, water soluble -, -, and -cdx-Ep and ethyleneglycol-bis(epoxy-propyl) ether products. The inclusion shifts were compared with each other and with the dioxane-induced solvent shift of MO. TheN, N-dimethyl-aniline side of MO shifted to a higher field site with the increase of the inner diameter in cdx. By substituting cdx with ether groups of different length, the mechanism of inclusion formation remains substantially the same, but by lengthening the hydrophobic cavity, the hydrophobic interaction becomes stronger, as a better resemblance of inclusion shifts and solvent shifts can be observed.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986. 相似文献
6.
Mitsuko Masutani Miyoko Ikejima Sofia Mariotto Tadashige Nozaki Shoichiro Kurata Shunji Natori Hiroyasu Esumi M. J. A Takashi Sugimura 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2004,80(7):336
To elucidate the physiological role of poly(ADP-ribose) polymerase (PARP), we studied the levels of PARP mRNA and protein during the developmental stages of Sarcophaga peregrina. PARP mRNA expression changed remarkably throughout the developmental stages. The level of PARP mRNA (the molecular ratio of PARP mRNA to the total RNA) was highest in unfertilized eggs and that of PARP protein (the molecular ratio of PARP protein to the total protein of the crude extract) was high in unfertilized and fertilized eggs and in 1st instar larvae. During the embryogenesis period, the levels of PARP mRNA and protein gradually decreased. The levels of PARP mRNA during larval and pupal periods became less than about 5% of that in unfertilized eggs. After the emergence of adult flies, the levels of PARP mRNA and protein increased both in female and male flies. PARP activity normalized with the total amount of protein in the crude extract changed in parallel to the level of PARP protein throughout the developmental stages. The biological significance of the drastic change of mRNA and protein levels of PARP still remains to be clarified. 相似文献
7.
Synthesis of the model compounds of carzinophilin carrying 2-methylidene-1-aza-bicyclo[3.1.0]hexane systems was achieved. Formation of malonylidenes or N-acyl-glycinylidenepyrrolidines was carried out by utilizing Eschenmoser's sulfide contraction or Herdeis's condensation between the 2-methylthio-Δ1-pyrrolone derivatives and ethyl nitroacetate, respectively. The 1-azabicyclo-[3.1.0]hexane systems were constructed by base-promoted aziridine formation. 相似文献
8.
Miyoko Suzuki Éva Fenyvesi Mária Szilasi József Szejtli Márton Kajtár Béla Zsadon Yoshio Sasaki 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(3-4):715-724
Circular dichroism (CD) and visible spectra of inclusion compounds between Methyl Orange (MO) analogues and -, -, -cyclodextrin (cdx), 2,6-dimethyl-and 2,3,6-trimethyl--cdx, water soluble -, -, -cdx polymer products were investigated. In the CD-spectroscopic investigation, the complex with -cdx epichlorohydrin condensate showed a large amplitude and splitting of the induced * band. Fractions of glyceryl ether of less than 2000 and polymer of more than 10000 dalton molecular mass were separated. Complexes of above two fractions and MO showed the same splitting spectral pattern. Job's plots from visible spectra showed the formation of the 11 complex and CD-data suggested the co-existence of the 21 MO-cdx complex. This splitting pattern showed the reversal of the signs when -cdx-ethyleneglycol-bis(epoxypropyl) ether was used and disappeared when larger host molecules and azo dyes were used. The splitting was explained by exciton interaction. 相似文献
9.
Conflicting pecificities were observed in electro-chemical 2e-reductions of NAD+ analogs: 1-phenyl-3-aminocarbonylpyridiniums gave quantitatively 1,4-dihydronicotinamides whereas 1-benzyl and 1-methyl derivatiives gave 1,6-isomers. 相似文献
10.