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101.
Mariko Matsunaga Makoto Nagasaka Takuya Nakanishi Takahiro Sawaguchi Tetsuya Osaka 《Electroanalysis》2008,20(9):955-962
The effect of pH on the enantiospecificity of Au (111) electrode modified with L ‐homocysteine was evaluated for the electrochemical redox reaction of 3,4‐dihydroxyphenylalanine (DOPA). Cyclic voltammetric peaks clearly exhibited enantiospecificity at pH 0.6 and 2, whereas no enantiospecificity was observed at pH 3, 4, and 5.5. Scanning tunneling microscopy confirmed the highly ordered (2√3×3√3)R30° structure of L ‐homocysteine at pH 0.6, at which L ‐homocysteine molecules form a dimer through the hydrogen‐bond between carboxy groups (COOH), while a disordered structure was observed at pH 5.5. These results suggest that the dimer formed in the acidic solutions at pH below 3 plays an important role in providing the enantiospecificity to the Au(111) surface. 相似文献
102.
Ito S Ando M Nomura A Morita N Kabuto C Mukai H Ohta K Kawakami J Yoshizawa A Tajiri A 《The Journal of organic chemistry》2005,70(10):3939-3949
[structure: see text] This paper describes the cyclotrimerization reaction of di(2-azulenyl)acetylenes (2a,b) catalyzed by Co2(CO)8 to produce hexa(2-azulenyl)benzene derivatives (1a,b). The cyclooligomerization of 2a and 2b utilizing CpCo(CO)2 as a catalyst produced (eta5-cyclopentadienyl)[tetra(2-azulenyl)cyclobutadiene]cobalt complexes (3a,b). The redox behavior of hexakis(6-octyl-2-azulenyl)benzene (1b), bis(6-octyl-2-azulenyl)acetylene (2b), and the cobalt complexes 3a and 3b along with 6-octyl-2-phenylazulene (19) was examined by cyclic voltammetry (CV). The reduction of compound 1b exhibited multiple-electron transfers in one step upon CV with a reduction potential similar to that of compound 19. However, the CVs of compounds 2b, 3a, and 3b were characterized by stepwise waves because of the reduction of each azulene ring. The mesomorphic behaviors of 1b, 2b, and 19 were also studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques. A new series of azulene derivatives, 1b, 2b, and 19, substituted by a long alkyl chain at the 6-position shows mesomorphism with crystalline polymorphs. Compound 1b showed a large temperature range of hexagonal columnar mesophases (Col(ho)) from 115.5 to 199.9 degrees C. Compound 2b has rectangular columnar (Col(ro)), smectic E (S(E)), and nematic (N) mesophases. Compound 19 exhibited an S(E) mesophase. 相似文献
103.
Tunneling splittings in the water trimer have been determined by the semiclassical WKB method, based on pathways characterized at the computational level of second-order M?ller-Plesset theory with basis sets of aug-cc-pVTZ quality. This calculation takes into account the single-flip and bifurcation tunneling rearrangements of the water trimer. The predicted splittings are 37.93 cm(-1) for the flip and 6.50x10(-3) cm(-1) for bifurcation, which agree quite well with the corresponding experimental values of 43.52 cm(-1) and 9.63x10(-3) cm(-1). 相似文献
104.
Mariko Ishiwatari 《Journal of Analytical and Applied Pyrolysis》1980,2(2):153-167
β-Carotene has ben heated under vacuum at temperatures ranging from 200 to 350°C for 24 h as a model of geothermal reaction of carotenoids in sediments and of a thermal reaction of highly conjugated polyene. Compounds with molecular weights of 138, 240, 346 and 444 and isomers of β-carotene were obtained in addition to toluene, xylene, ionene and 2,6-dimethylnaphthalene, which have been reported previously as pyrolysis products of β-carotene. Possible reaction mechanisms for the formation of the pyrolysis products are given. 相似文献
105.
106.
Hasegawa T Fujisawa T Numata M Umeda M Matsumoto T Kimura T Okumura S Sakurai K Shinkai S 《Chemical communications (Cambridge, England)》2004,(19):2150-2151
Single-walled carbon nanotubes can be entrapped within a helical superstructure composed of schizophyllan bearing lactoside-appendages to show an excellent water-solubility as well as a specific lectin-affinity. 相似文献
107.
Hasegawa T Umeda M Matsumoto T Numata M Mizu M Koumoto K Sakurai K Shinkai S 《Chemical communications (Cambridge, England)》2004,(4):382-383
A schizophyllan (beta-1,3-glucan) derivative carrying lactose-appendages prepared by reductive amination can form stable macromolecular complexes with polynucleotides, shows excellent affinity with a lactose-binding lectin, and effectively mediates gene transfection into hepatocytes. 相似文献
108.
Banno N Nakanishi T Matsunaga M Asahi T Osaka T 《Journal of the American Chemical Society》2004,126(2):428-429
Enantioselective crystal growth of leucine occurs on a solid surface modified with a self-assembled monolayer depending on the chirality of the enantiomer attached, as evidenced by the X-ray diffraction method. 相似文献
109.
Aimi N Kitajima M Yokoya M Takayama H Sakamoto S Yamaguchi K 《Chemical & pharmaceutical bulletin》2002,50(11):1528-1529
The fragmentation from beta-carboline-type monoterpenoid glucoindole alkaloids to harman, which is a hypothetical pathway to generate simple beta-carbolines, was actualized in the collision-induced dissociation in MS. 相似文献
110.
Lead tetraacetate oxidation of a Corynanthe-type indole alkaloid, mitragynine, produced mainly 7-acetoxyindolenine derivative (2) together with a dimeric compound (4) as a minor product. The novel structure having a bridge between the C-11' and C-7 positions in the respective indolenine parts and its formation mechanism were studied. 相似文献