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631.
[reaction: see text]. Chalcone synthase (CHS) is a plant-specific type III polyketide synthase catalyzing condensation of 4-coumaroyl-CoA with three molecules of malonyl-CoA. Surprisingly, it was demonstrated that S338V mutant of Scutellaria baicalensis CHS produced octaketides SEK4/SEK4b from eight molecules of malonyl-CoA. Further, the octaketides-forming activity was dramatically increased in a CHS triple mutant (T197G/G256L/S338T). The functional conversion is based on the simple steric modulation of a chemically inert residue lining the active-site cavity. 相似文献
632.
Tsuyoshi Satoh Shotaro Ikeda Toshifumi Miyagawa Takafumi Noguchi 《Tetrahedron letters》2010,51(15):1955-1084
1-Chlorocyclopropyl p-tolyl sulfoxides bearing an alkoxymethyl group at the 2-position were easily prepared from α,β-unsaturated esters with dichloromethyl p-tolyl sulfoxide and alkylhalides in three steps in good overall yields. Treatment of the 1-chlorocyclopropyl p-tolyl sulfoxides with i-PrMgCl resulted in the formation of 3-oxabicyclo[3.1.0]hexanes in up to 89% yield as a single diastereomer via the 1,5-CH insertion reaction of the generated cyclopropylmagnesium carbenoid intermediates. This procedure provides a good way for the synthesis of 3-oxabicyclo[3.1.0]hexanes from α,β-unsaturated esters in only four steps. 3-Aza- and 3-thiabicyclo[3.1.0]hexanes were also obtained from the corresponding precursors via the 1,5-CH insertion reaction of the cyclopropylmagnesium carbenoid intermediates, though the yields were low to moderate. 相似文献
633.
Mitsuhiro Kanakubo Takafumi Aizawa Hiroshi Nanjo Yasuo Kameda Yuko Amo Takeshi Usuki 《Fluid Phase Equilibria》2010
X-ray diffraction measurements for the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], mixed with CO2 were carried out at high pressures using our developed polymer cell. The intermolecular distribution functions obtained for [BMIM][BF4]–CO2 mixtures showed that CO2 molecules are preferentially solvated to the [BF4]− anion. The similar preferential solvation was previously observed in analogous 1-btuyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF6], with a different anion, which is in harmony with the present results in [BMIM][BF4]–CO2. 相似文献
634.
Polyaniline (PANI) microspheres were prepared by electrochemical polymerization. To obtain PANI having novel micro- and nanostructures,
by the potential scan technique, aniline was electropolymerized in the presence of DNA using four polymerizing solutions containing
different acids: H2SO4, C6H5SO3H, HClO4, and CF3COOH. The growth rate of the PANI film on the electrode surface decreased by the presence of DNA, suggesting that DNA interacted
with the growing PANI molecules during the electropolymerization. The growth rate also depended on the type of acid, i.e.,
the anion, in the polymerizing solution and was in the order of SO4
2− > C6H5SO3
− > ClO4
− > CF3COO−, which significantly coincided with the reverse order of the Hofmeister series representing the lyophilicity of the anion.
When aniline was electropolymerized in the CF3COOH polymerizing solution containing DNA, PANI microspheres were obtained without any templates. This PANI showed a sufficient
redox activity in the less acidic solution in which the ordinary PANI has a slight redox activity. On the other hand, the
electronic state of the PANI differed from the ordinary ones; a new absorption band was evident at 620 nm. The difference
in the redox activity and electronic state suggested that the DNA molecules were incorporated in the PANI and electronically
interacted with the PANI molecules. 相似文献
635.
We show that image simulation is invaluable for the interpretation of time-dependent environmental transmission electron microscopy (ETEM) images. Experimental ETEM images of a crystalline nanoparticle catalyst (NPC) during the growth of carbon nanotubes were compared with simulated images of the Fe(21)Mo(2)C(6) structure that was observed along various directions. Lattice images that appear in the NPC at different times can be accounted for by considering only the Fe(21)Mo(2)C(6) structure. 相似文献
636.
Seok Kyu Han Jung-Hyun Kim Soon-Ku Hong Jae-Ho Song Jung-Hoon Song Jae Wook Lee Jeong Yong Lee Sun Ig Hong Takafumi Yao 《Journal of Crystal Growth》2010,312(15):2196-2200
Structural and optical properties of nonpolar a-plane ZnO films grown with different II/VI ratios on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy were investigated. Even by increasing the II/VI ratio across the stoichiometric flux condition a consistent surface morphology of striated stripes along the ZnO 〈0 0 0 1〉 direction without any pit formation was observed, which is contrary to polar c-plane ZnO films. Root mean square surface roughness, full width at half maximum values of X-ray rocking curves, defect densities, and photoluminescence were changed with the II/VI ratio. The sample grown with stoichiometric flux condition showed the lowest value of rms roughness, the smallest threading dislocation and stacking fault densities of ∼4.7×108 cm−2 and ∼9.5×104 cm−1, respectively, and the highest intensity of DoX peak. These results imply that the stoichiometric flux growth condition is suitable to obtain superior structural and optical properties compared to other flux conditions. 相似文献
637.
638.