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91.
Yoshitane Imai Takafumi Kinuta Nobuo Tajima Yoshio Matubara 《Tetrahedron letters》2006,47(21):3603-3606
By using three types of viologen derivatives, we synthesized chiral charge-transfer (CT) complexes with an axially chiral 1,1′-bi-2-naphthol molecule and successfully controlled the crystal structure and inclusion ability of the third component by changing the viologens. 相似文献
92.
Takafumi Shido Takumi Okazaki Masaru Ichikawa 《Journal of molecular catalysis. A, Chemical》1997,120(1-3):33-45
Structure and catalytic activity of Ir4(CO)12 bound to tris-(hydroxymethyl)phosphine (THP) grafted silica (THP/SiO2) was investigated by means of EXAFS, FT-IR and kinetic studies. It was found that Ir4(CO)12 was uniformly attached on THP/SiO2 by substitution of CO by THP (Ir4/THP/SiO2). The tetra-iridium carbonyl cluster framework was remained during the substitution of THP ligands and two THP ligands coordinated to the iridium carbonyl clusters to form Ir4(CO)10(THP/SiO2)2. species. When Ir4/THP/SiO2 was evacuated at 373 K, bridge CO was desorbed and Debye-Waller factor of Ir---Ir contribution derived from EXAFS analysis was increased which suggested that the cluster framework was distorted by the evacuation at 373 K. The resulting sample evacuated at 373 K was an active catalyst for hydroformylation of ethene and partial oxidation of propene, while the Ir4/THP/SiO2 without evacuation exhibited poor catalytic activities. The propene oxidation reaction proceed on the Ir4/THP/SiO2 evacuated at 323–353 K under subatmospheric pressures to give acetone as a product in high selectivity. The ethene hydroformylation proceed on the evacuated Ir4/THP/SiO2 at lower temperatures compared with other conventional iridium catalysts. EXAFS characterization and kinetic studies suggested that the catalytic activities were associated with the structural distortion of the iridium cluster framework due to surface attachment by the bidentate phosphine substitution. 相似文献
93.
Three antibiotics with a common structural feature as prenylated phenols were synthesized: (±)-ascochlorin (5 - chloro-2,4 - dihydroxy - 6 - methyl - 3 - [(2E',4/E') - 5' - (1′,2′,6′ - trimethyl - 3′-oxocyclohexyl) - 3' - methyl - 2',4' - p benzaldehyde), (±)-ascofuranone (5 - chloro - 2,4 - dihydroxy - 6 - methyl - 3 - [(2'E,6'E) - 7' - (3′,3′ - dimethyl - 4′ - oxo - 2′ - oxacyclopentyl) - 3',7 -dimethyl - 2',6' - heptadienyl] benzaldehyde) and LL-Z1272α (5 - chloro - 2,4 - dihydroxy - 6 - methyl -3 - [(2'E,6'E) - 3',7',11' - trimethyl - 2',6', 10' - dodecatrienyl] benzaldehyde) 相似文献
94.
95.
A poly(amine ester) dendrimer with naphthyl units (G1N6) has been synthesized as a fluorescent chemosensor for metal ions. We investigated the metal-ion recognition of G1N6 by adding each of Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Co(2+), Cu(2+), Fe(3+), Mg(2+), Ni(2+), and Zn(2+) in acetonitrile solution. Large changes were observed in the fluorescence spectra of G1N6 upon the addition of Al(3+), Cu(2+), and Zn(2+). 相似文献
96.
97.
Jun Fukuda Takafumi Iwura Shigehiro Yanagihara Kenji Kano 《Analytical and bioanalytical chemistry》2014,406(25):6257-6264
Hollow-fiber-flow field-flow fractionation (HF5) separates protein molecules on the basis of the difference in the diffusion coefficient, and can evaluate the aggregation ratio of proteins. However, HF5 is still a minor technique because information on the separation conditions is limited. We examined in detail the effect of different settings, including the main-flow rate, the cross-flow rate, the focus point, the injection amount, and the ionic strength of the mobile phase, on fractographic characteristics. On the basis of the results, we proposed optimized conditions of the HF5 method for quantification of monoclonal antibody in sample solutions. The HF5 method was qualified regarding the precision, accuracy, linearity of the main peak, and quantitation limit. In addition, the HF5 method was applied to non-heated Mab A and heat-induced-antibody-aggregate-containing samples to evaluate the aggregation ratio and the distribution extent. The separation performance was comparable with or better than that of conventional methods including analytical ultracentrifugation–sedimentation velocity and asymmetric-flow field-flow fractionation. 相似文献
98.
Arief Budi Witarto Takafumi Ohtera Koji Sode 《Applied biochemistry and biotechnology》1999,77(1-3):159-168
We have previously reported that a chimeric pyrroloquinoline quinone (PQQ) glucose dehydrogenase (GDH), E97A3, which was made
up of 97% of Escherichia coli PQQGDH sequence and 3% of Acinetobacter calcoaceticus PQQGDH, showed increased thermal stability compared with both parental enzymes. Site-directed mutagenesis studies were carried
out in order to investigate the role of amino-acid substitution at the C-terminal region, Ser 771, of a chimeric PQQGDHs on
their thermal stability. A series of Ser 771 substitutions of a chimeric PQQGDH, E99A1, confirmed that hydrophobic interaction
governs the thermal stability of the chimeric enzymes. Comparison of the thermal denaturation of E. coli PQQGDH and E97A3 followed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy revealed that E97 A3 acquired stability
at the first step of denaturation, which is reversible, and where no significant secondary structure change was observed.
These results suggested that the interaction between C-terminal and N-terminal regions may play a crucial role in maintaining
the overall structure of β-propeller proteins. 相似文献
99.
Revisiting the Bromination of CH Bonds with Molecular Bromine by Using a Photo‐Microflow System
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Dr. Yoshiyuki Manabe Yuriko Kitawaki Masahiro Nagasaki Prof. Koichi Fukase Prof. Hiroshi Matsubara Yoshiko Hino Prof. Takahide Fukuyama Prof. Ilhyong Ryu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12750-12753
The photobromination of C?H bonds by using molecular bromine was reinvestigated under microfluidic conditions. The continuous‐flow method suppressed the production of dibrominated compounds and effectively produced the desired monobrominated products with high selectivity. Rapid bromination of benzylic substrates containing a photoaffinity azide group was achieved without any decomposition. 相似文献
100.
J. Alberto Rodríguez‐Velamazán Dr. Chiara Carbonera Dr. Miguel Castro Dr. Elías Palacios Dr. Takafumi Kitazawa Prof. Dr. Jean‐François Létard Prof. Dr. Ramón Burriel Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8785-8796
In the series of polymeric spin‐crossover compounds Fe(X‐py)2[Ag(CN)2)]2 (py=pyridine, X=H, 3‐Cl, 3‐methyl, 4‐methyl, 3,4‐dimethyl), magnetic and calorimetric measurements have revealed that the conversion from the high‐spin (HS) to the low‐spin (LS) state occurs by two‐step transitions for three out of five members of the family (X=H, 4‐methyl, and X=3,4‐dimethyl). The two other compounds (X=3‐Cl and 3‐methyl) show respectively an incomplete spin transition and no transition at all, the latter remaining in the HS state in the whole temperature range. The spin‐crossover behaviour of the compound undergoing two‐step transitions is well described by a thermodynamic model that considers both steps. Calculations with this model show low cooperativity in this type of systems. Reflectivity and photomagnetic experiments reveal that all of the compounds except that with X=3‐methyl undergo light‐induced excited spin state trapping (LIESST) at low temperatures. Isothermal HS‐to‐LS relaxation curves at different temperatures support the low‐cooperativity character by following an exponential decay law, although in the thermally activated regime and for aX=H and X=3,4‐dimethyl the behaviour is well described by a double exponential function in accordance with the two‐step thermal spin transition. The thermodynamic parameters determined from this isothermal analysis were used for simulation of thermal relaxation curves, which nicely reproduce the experimental data. 相似文献