The Experts below are selected from a list of 156 Experts worldwide ranked by ideXlab platform
R.bruce Lennox - One of the best experts on this subject based on the ideXlab platform.
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Pyrroloquinolinequinone enzyme electrode based on the coupling of methanol dehydrogenase to a tetrathiafulvalene-tetracyanoquinodimethane electrode
Analytical Chemistry, 1991Co-Authors: Shishan. Zhao, R.bruce LennoxAbstract:An enzyme electrode based on the coupling of a PQQ-containing methanol dehydrogenase (EC 1.1.99.8) and the novel electrode material, TTF-TCNQ, is reported. Characterization of this enzyme electrode shows that the substrate-reduced enzyme is rapidly turned over by this electrode material, whereas no turnover is evident on a conventional (I.e., Pt) electrode. Enzyme properties (K m , T sensitivity, pH dependence) when interfaced to the electrode are reported, and the response characteristics of the resulting biosensor are summarized
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Pyrroloquinolinequinone enzyme electrode based on the coupling of methanol dehydrogenase to a tetrathiafulvalene-tetracyanoquinodimethane electrode
Analytical Chemistry, 1991Co-Authors: Shishan. Zhao, R.bruce LennoxAbstract:An enzyme electrode based on the coupling of a PQQ-containing methanol dehydrogenase (EC 1.1.99.8) and the novel electrode material, TTF-TCNQ, is reported. Characterization of this enzyme electrode shows that the substrate-reduced enzyme is rapidly turned over by this electrode material, whereas no turnover is evident on a conventional (I.e., Pt) electrode. Enzyme properties (K m , T sensitivity, pH dependence) when interfaced to the electrode are reported, and the response characteristics of the resulting biosensor are summarized
Takahiko Kojima - One of the best experts on this subject based on the ideXlab platform.
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controlling the redox properties of a Pyrroloquinolinequinone pqq derivative in a ruthenium ii coordination sphere
Dalton Transactions, 2015Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Kazunari Yoshizawa, Yoshihito Shiota, Takahiko KojimaAbstract:Ruthenium(II) complexes of PQQTME, a trimethyl ester derivative of redox-active PQQ (Pyrroloquinolinequinone), were prepared using a tridentate ligand, 2,2′:6′,2′′-terpyridine (terpy) as an auxiliary ligand. The characterization of the complexes was performed by spectroscopic methods, X-ray crystallography, and electrochemical measurements. In one complex, the pyridine site of PQQTME binds to the [RuII(terpy)] unit as a tridentate ligand, and a silver(I) ion is coordinated by the quinone moiety in a bidentate fashion. In contrast, another complex includes the [RuII(terpy)] unit at the bidentate quinone moiety of the PQQTME ligand. The difference in the coordination modes of the complexes exhibits a characteristic difference in the stability of metal coordination and also in the reversibility of the reduction processes of the PQQTME ligand. It should be noted that an additional metal-ion-binding to the PQQTME ligand largely raises the 1e−-reduction potential of the ligand. In addition, we succeeded in the characterization of the 1e−-reduced species of the complexes, where the unpaired electron was delocalized in the π-conjugated system of the PQQTME˙− ligand, using UV-Vis absorption and ESR spectroscopies.
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Heteronuclear RuIIAgI Complexes Having a Pyrroloquinolinequinone Derivative as a Bridging Ligand
Inorganic chemistry, 2013Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Yoshihiko Shiota, Kazunari Yoshizawa, Takahiko KojimaAbstract:Herein, we report the synthesis of a novel heterohexanuclear complex (1) of a heteroaromatic cofactor, Pyrroloquinolinequinone (PQQ). The crystal structure of 1 was determined to reveal that two PQQ-bridged RuIIAgI units were linked by two [AgI(OTf)2]− units (OTf = CF3SO3–). A solvent-bound RuIIAgI heterodinuclear complex (2) was formed from 1 in a coordinating solvent such as acetone to show an intense metal-to-ligand charge-transfer band at 709 nm.
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Heteronuclear RuIIAgI Complexes Having a Pyrroloquinolinequinone Derivative as a Bridging Ligand
2013Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Yoshihiko Shiota, Kazunari Yoshizawa, Takahiko KojimaAbstract:Herein, we report the synthesis of a novel heterohexanuclear complex (1) of a heteroaromatic cofactor, Pyrroloquinolinequinone (PQQ). The crystal structure of 1 was determined to reveal that two PQQ-bridged RuIIAgI units were linked by two [AgI(OTf)2]− units (OTf = CF3SO3–). A solvent-bound RuIIAgI heterodinuclear complex (2) was formed from 1 in a coordinating solvent such as acetone to show an intense metal-to-ligand charge-transfer band at 709 nm
Shishan. Zhao - One of the best experts on this subject based on the ideXlab platform.
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Pyrroloquinolinequinone enzyme electrode based on the coupling of methanol dehydrogenase to a tetrathiafulvalene-tetracyanoquinodimethane electrode
Analytical Chemistry, 1991Co-Authors: Shishan. Zhao, R.bruce LennoxAbstract:An enzyme electrode based on the coupling of a PQQ-containing methanol dehydrogenase (EC 1.1.99.8) and the novel electrode material, TTF-TCNQ, is reported. Characterization of this enzyme electrode shows that the substrate-reduced enzyme is rapidly turned over by this electrode material, whereas no turnover is evident on a conventional (I.e., Pt) electrode. Enzyme properties (K m , T sensitivity, pH dependence) when interfaced to the electrode are reported, and the response characteristics of the resulting biosensor are summarized
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Pyrroloquinolinequinone enzyme electrode based on the coupling of methanol dehydrogenase to a tetrathiafulvalene-tetracyanoquinodimethane electrode
Analytical Chemistry, 1991Co-Authors: Shishan. Zhao, R.bruce LennoxAbstract:An enzyme electrode based on the coupling of a PQQ-containing methanol dehydrogenase (EC 1.1.99.8) and the novel electrode material, TTF-TCNQ, is reported. Characterization of this enzyme electrode shows that the substrate-reduced enzyme is rapidly turned over by this electrode material, whereas no turnover is evident on a conventional (I.e., Pt) electrode. Enzyme properties (K m , T sensitivity, pH dependence) when interfaced to the electrode are reported, and the response characteristics of the resulting biosensor are summarized
Shinobu Itoh - One of the best experts on this subject based on the ideXlab platform.
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Photochemical Reactions of Coenzyme PQQ (Pyrroloquinolinequinone) and Analogues with Benzyl Alcohol Derivatives via Photoinduced Electron Transfer
Journal of the American Chemical Society, 2000Co-Authors: Shunichi Fukuzumi, Shinobu Itoh, Takashi Komori, Tomoyoshi Suenobu, Akito Ishida, And Mamoru Fujitsuka, Osamu ItoAbstract:Photochemical redox reactions of the trimethyl ester of coenzyme PQQ (PQQTME) with benzyl alcohol derivatives (ArCH2OH), tetrahydrofuran, and 1,4-cyclohexadiene occur efficiently under visible light irradiation in MeCN to yield PQQTMEH2 (reduced PQQTME in the quinol form) and the corresponding dehydrogenated products (ArCHO, furan, and benzene) quantitatively. A similar photochemical oxidation of benzyl alcohols also occurs with phenanthrolinequinone derivatives (PTQ), benzoquinolinequinone derivatives (BQQ), and phenanthrenequinone (PQ). PQQTME and the analogues are essentially nonfluorescent in MeCN, and the photochemical reaction of the o-quinones is retarded significantly in the presence of molecular oxygen. Transient absorption spectra of the triplet excited states of the o-quinones were detected in laser flash photolysis of the MeCN solutions. From the decay of T−T spectra were determined the lifetimes of the triplet excited states of the o-quinones. The quenching rate constants of the triplet excit...
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Redox Catalysis of Novel Heterocyclic o -Quinone Coenzymes
Novel Trends in Electroorganic Synthesis, 1998Co-Authors: Shinobu Itoh, Hirokatsu Kawakami, Shunichi FukuzumiAbstract:Quinones have been widely utilized as a redox catalyst or an electrochemical mediator in a variety of chemical reactions and electrochemical devices. In order to achieve high catalytic efficiency of such systems, developement of a highly reactive and robust catalyst is crucial. In this context, we have recently developed a series of heterocyclic o-quinone compounds that mimic the structures and functions of newly found coenzymes such as Pyrroloquinolinequinone (PQQ) and tryptophan tryptophylquinone (TTQ).1 Here, we demonstrate that a calcium complex of a PQQ analog acts as a very efficient catalyst for the oxidation of simple alcohols such as methanol and ethanol under a very mild condition.2
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The photochemical oxidation of benzyl alcohols by the triplet excited state of coenzyme Pyrroloquinolinequinone
Chemical Communications, 1996Co-Authors: Shinobu Itoh, Takashi Komori, Yutaka Chiba, And Akito Ishida, Setsuo Takamuku, Shunichi FukuzimiAbstract:The first example of the photochemical reaction of coenzyme Pyrroloquinolinequinone (PQQ) with benzyl alcohols is reported, where the triplet excited state of PQQ is the active species which oxidises alcohols to the corresponding aldehydes; the mechanism of the photochemical redox reaction between PQQ and benzyl alcohols is discussed.
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C-4 and C-5 adducts of cofactor PQQ (Pyrroloquinolinequinone). Model studies directed toward the action of quinoprotein methanol dehydrogenase
Journal of the American Chemical Society, 1993Co-Authors: Shinobu Itoh, Yoshifumi Fukui, Hiroshi Murao, Masaki Ogino, Mitsuo Komatsu, Tsuyoshi Inoue, Yoshiki Ohshiro, Nobutami KasaiAbstract:Methanol addition to the trimethyl ester of cofactor PQQ (PQQTME) was investigated in detail to obtain information on the action of quinoprotein methanol dehydrogenase. The hemiacetal-type adduct was easily isolated from a methanol solution of PQQTME. The crystal structure of the adduct was determined by X-ray diffraction for the first time, showing that methanol addition occurred at the S-position (C-S) of the quinone as in the case of the acetone adduct formation. On the other hand, treatment of PQQTME in methanol under acidic conditions gave the dimethyl acetal derivative as a major product for which the addition position of methanol was determined to be C-4 by X-ray crystallographic analysis
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Chemical Functions of Novel Heterocyclic o-Quinone Cofactors and Their Applications
Journal of Synthetic Organic Chemistry Japan, 1993Co-Authors: Shinobu ItohAbstract:The chemical functions of novel heterocyclic o-quinone cofactors, PQQ (Pyrroloquinolinequinone) and TTQ (tryptophan tryptophylquinone), and their derivatives were investigated from the viewpoints of synthetic organic chemistry. PQQ was found to be a good catalyst in the aerobic oxidation of biologically important substances such as amines, amino acids, thiols, glucose, NADH, and so on. Studies on the structure-reactivity relationships and product analyses provided a lot of important information on the structural importance of PQQ and on the oxidation reaction mechanisms. In particular, the reaction of PQQ and methanol was examined in detail to suggest that the enzymatic oxidation of methanol proceeds via an ionic mechanism through the C-4 acetal intermediate. PQQ and its related compounds were also found to act as an efficient mediator in the electrochemical oxidation of NADH and the electrochemical reduction of O2, which could be coupled with enzymatic redox reactions. An efficient enzymatic redox reaction in organic solvents was also constructed by applying PQQ as an electron transfer catalyst. The model compound of the newly found cofactor TTQ was synthesized for the first time and its physicochemical properties and chemical functions were found to be very close to those of the native enzyme.
Hiroumi Mitome - One of the best experts on this subject based on the ideXlab platform.
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controlling the redox properties of a Pyrroloquinolinequinone pqq derivative in a ruthenium ii coordination sphere
Dalton Transactions, 2015Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Kazunari Yoshizawa, Yoshihito Shiota, Takahiko KojimaAbstract:Ruthenium(II) complexes of PQQTME, a trimethyl ester derivative of redox-active PQQ (Pyrroloquinolinequinone), were prepared using a tridentate ligand, 2,2′:6′,2′′-terpyridine (terpy) as an auxiliary ligand. The characterization of the complexes was performed by spectroscopic methods, X-ray crystallography, and electrochemical measurements. In one complex, the pyridine site of PQQTME binds to the [RuII(terpy)] unit as a tridentate ligand, and a silver(I) ion is coordinated by the quinone moiety in a bidentate fashion. In contrast, another complex includes the [RuII(terpy)] unit at the bidentate quinone moiety of the PQQTME ligand. The difference in the coordination modes of the complexes exhibits a characteristic difference in the stability of metal coordination and also in the reversibility of the reduction processes of the PQQTME ligand. It should be noted that an additional metal-ion-binding to the PQQTME ligand largely raises the 1e−-reduction potential of the ligand. In addition, we succeeded in the characterization of the 1e−-reduced species of the complexes, where the unpaired electron was delocalized in the π-conjugated system of the PQQTME˙− ligand, using UV-Vis absorption and ESR spectroscopies.
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Heteronuclear RuIIAgI Complexes Having a Pyrroloquinolinequinone Derivative as a Bridging Ligand
Inorganic chemistry, 2013Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Yoshihiko Shiota, Kazunari Yoshizawa, Takahiko KojimaAbstract:Herein, we report the synthesis of a novel heterohexanuclear complex (1) of a heteroaromatic cofactor, Pyrroloquinolinequinone (PQQ). The crystal structure of 1 was determined to reveal that two PQQ-bridged RuIIAgI units were linked by two [AgI(OTf)2]− units (OTf = CF3SO3–). A solvent-bound RuIIAgI heterodinuclear complex (2) was formed from 1 in a coordinating solvent such as acetone to show an intense metal-to-ligand charge-transfer band at 709 nm.
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Heteronuclear RuIIAgI Complexes Having a Pyrroloquinolinequinone Derivative as a Bridging Ligand
2013Co-Authors: Hiroumi Mitome, Tomoya Ishizuka, Yoshihiko Shiota, Kazunari Yoshizawa, Takahiko KojimaAbstract:Herein, we report the synthesis of a novel heterohexanuclear complex (1) of a heteroaromatic cofactor, Pyrroloquinolinequinone (PQQ). The crystal structure of 1 was determined to reveal that two PQQ-bridged RuIIAgI units were linked by two [AgI(OTf)2]− units (OTf = CF3SO3–). A solvent-bound RuIIAgI heterodinuclear complex (2) was formed from 1 in a coordinating solvent such as acetone to show an intense metal-to-ligand charge-transfer band at 709 nm
