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171.
The direct electrochemistry of myoglobin (Mb) has been observed at a glassy carbon (GC) electrode coated with silica sol-gel-encapsulated Mb film. A well-behaved cyclic voltammogram is observed with a midpoint potential (E(1/2)) of -0.25 V vs Ag/AgCl in a pH 7.0 phosphate buffer. This potential, which is pH-dependent, is 70-90 mV more negative than the formal potential values obtained by using the spectroeletrochemical titration method at the same pH. Square wave voltametry (SWV) also shows a peak potential of -0.25 V for the reduction of Mb under the same experimental conditions. Both cathodic and anodic peak currents have a linear relationship with the scan rate. The midpoint potential decreases with pH, having a slope of -30 mV/pH. UV-vis and resonance Raman spectroscopic studies reveal that the sol-gel provides a bio-compatible environment where Mb retains a structure similar to its solution form, a 6-coordinated aquomet myoglobin. These results suggest that the silica sol-gel is a useful matrix for studying direct electrochemistry of other heme proteins. 相似文献
172.
Treatment of [[Ru(P(OCH3)3)2(CH3CN)3]2(mu-Q2)](CF3SO3)4 (1, Q = S; 2, Q = Se) with haloalkenes resulted in the formation of complexes carrying unsaturated C3Q2 five-membered or C4Q2 six-membered rings via elimination of HX (X = Cl, Br). The reactions of 1 and 2 with allyl bromide gave the corresponding addition products, [[Ru(P(OCH3)3)2(CH3CN)3]2(mu-QCH=CHCH2Q)](CF3SO3)4 (3, Q = S; 4, Q = Se), via elimination of HBr. The elimination process seems to be thermodynamically controlled and takes place at the final stage of the reaction. The steric effect of the halogen atoms seems more operative than the electronic one. 相似文献
173.
Production mechanism of active species on the oxidative bromination following perhydrolase activity
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Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br?. Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br? and the strong brominating power with some tolerance against H2O2. Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
174.
Discovery and Total Synthesis of Streptoaminals: Antimicrobial [5,5]‐Spirohemiaminals from the Combined‐Culture of Streptomyces nigrescens and Tsukamurella pulmonis
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Dr. Ryosuke Sugiyama Dr. Shinichi Nishimura Dr. Taro Ozaki Dr. Shumpei Asamizu Prof. Dr. Hiroyasu Onaka Prof. Dr. Hideaki Kakeya 《Angewandte Chemie (International ed. in English)》2016,55(35):10278-10282
A series of lipidic spirohemiaminals, designated streptoaminals, is reported. These were discovered by surveying the unique molecular signatures identified in the mass spectrometry data of the combined‐culture broth of Streptomyces nigrescens HEK616 and Tsukamurella pulmonis TP‐B0596. Mass spectrometry analysis showed that streptoaminals appeared as a cluster of ion peaks, which were separated by 14 mass unit intervals, implying the presence of alkyl chains of different lengths. The chemical structures of these compounds were elucidated by spectroscopic analysis and total synthesis. Streptoaminals with globular structures showed broad antimicrobial activities, whereas the planar structures of the 5‐alkyl‐1,2,3,4‐tetrahydroquinolines found in the same combined‐culture did not. This work shows the application of microbes as reservoirs for a range of chemical scaffolds. 相似文献
175.
Oxidation Ability of Plasmon‐Induced Charge Separation Evaluated on the Basis of Surface Hydroxylation of Gold Nanoparticles
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Dr. Hiroyasu Nishi Prof. Tetsu Tatsuma 《Angewandte Chemie (International ed. in English)》2016,55(36):10771-10775
The oxidation ability of plasmonic photocatalysts, which has its origins in plasmon‐induced charge separation and has not yet been studied quantitatively and systematically, is important for designing practical photocatalytic systems. Oxidation ability was investigated on the basis of surface hydroxylation of Au nanoparticles on TiO2 at various irradiation wavelengths and electrolyte pH values. The reaction proceeds only when the sum of the flat band potential of TiO2 and the irradiated photon energy is close to, or more positive than, the theoretical potential for the reaction. 相似文献
176.
Yuta Yamamoto Dr. Kan Wakamatsu Dr. Tetsuo Iwanaga Dr. Hiroyasu Sato Prof. Dr. Shinji Toyota 《化学:亚洲杂志》2016,11(9):1370-1375
A macrocyclic compound consisting of six 2,7‐anthrylene units was successfully synthesized by Ni‐mediated coupling of the corresponding dibromo precursor as a novel π‐conjugated compound. This compound was sufficiently stable and soluble in organic solvents due to the presence of mesityl groups. X‐ray analysis showed that the molecule had a nonplanar and hexagonal wheel‐shaped framework of approximately S6 symmetry. The dynamic process between two S6 structures was observed by using the dynamic NMR technique, the barrier being 58 kJ mol?1. The spectroscopic properties of the hexamer were compared with those of analogous linear oligomers. 相似文献
177.
Furukawa H Kim J Ockwig NW O'Keeffe M Yaghi OM 《Journal of the American Chemical Society》2008,130(35):11650-11661
Metal-organic polyhedra and frameworks (MOPs and MOFs) were prepared by linking square units M2(CO2)4 (M = Cu and Zn) with a variety of organic linkers designed to control the dimensionality (periodicity) and topology of the resulting structures. We describe the preparation, characterization, and crystal structures of 5 new MOPs and 11 new MOFs (termed MOP-14, -15, -17, -23, -24 and MOF-114, -115, -116, -117, -118, -119, -222, -601, -602, -603, -604) and show how their structures are related to the shape and functionality of the building blocks. The gas uptake behaviors of MOP-23 and MOF-601 to -603 are also presented as evidence that these structures have permanent porosity and rigid architectures. 相似文献
178.
179.
Shunji H Yoshikatsu T Akihiro F Hiroyasu I Kiyoshi T Yasuyuki S Masa-aki U Akihiko K Kazuo T Hideyuki O Katsunori A 《Journal of chromatography. A》2008,1178(1-2):187-198
Polychlorinated dibenzo-p-dioxins and dibenzofurans in crude extracts of fly ash and flue gas from municipal waste incinerators were quantified using a comprehensive multidimensional gas chromatograph (GC x GC) coupled to a high-resolution time-of-flight mass spectrometer (HR-TOFMS). For identification and quantification, we developed our own program to prepare 3D chromatograms of selected mass numbers from the data of the GC x GC/HR-TOFMS. Isolation of all congeners with a TCDD toxic equivalency factor from the other isomers by only one injection was confirmed. The instrumental detection limit of TCDD on the GC x GC/HR-TOFMS was 0.9 pg by the relative calibration method. Quantification of these substances in the crude extracts was achieved by direct injection to the GC x GC/HR-TOFMS. The results agree with the values obtained using a generic gas chromatography/high-resolution mass spectrometry (GC/HRMS) system. It was confirmed that measurement by high-resolution TOFMS and GC x GC effectively reduces interference from other chemicals. 相似文献
180.
Han SS Furukawa H Yaghi OM Goddard WA 《Journal of the American Chemical Society》2008,130(35):11580-11581
We report the H2 uptake properties of six covalent organic frameworks (COFs) from first-principles-based grand canonical Monte-Carlo simulations. The predicted H2 adsorption isotherm is in excellent agreement with the only available experimental result (3.3 vs 3.4 wt % at 50 bar and 77 K for COF-5), also reported here, validating the predictions. We predict that COF-105 and COF-108 lead to a reversible excess H2 uptake of 10.0 wt % at 77 K, making them the best known storage materials for molecular hydrogen at 77 K. We predict that the total H2 uptake for COF-108 is 18.9 wt % at 77 K. COF-102 shows the best volumetric performance, storing 40.4 g/L of H2 at 77 K. These results indicate that the COF systems are most promising candidates for practical hydrogen storage. 相似文献