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Matthias Wagner - One of the best experts on this subject based on the ideXlab platform.
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steric shielding vs structural constraint in a boron containing Polycyclic Aromatic Hydrocarbon
Organometallics, 2017Co-Authors: Valentin M Hertz, Naoki Ando, Masato Hirai, Michael Bolte, Hans-wolfram Lerner, Shigehiro Yamaguchi, Matthias WagnerAbstract:The highly reactive boron-doped Polycyclic Aromatic Hydrocarbon 8H-8-bromo-8-borabenzo[gh]tetraphene has been synthesized via a multistep sequence encompassing a Peterson olefination, a stilbene-type photocyclization, and an Si/B exchange reaction. The compound was subsequently treated with mesityllithium to give the derivative 3 or with [2,6-bis(propen-2-yl)phenyl]lithium to furnish the intermediate 4. A scandium(III) triflate mediated Friedel–Crafts reaction transformed 4 into the rigid, planarized triarylborane 5. Compounds 3 and 5 are both inert toward air and moisture but are still able to bind fluoride ions, where the affinity of 3 in CHCl3 is higher than that of 5. Both arylboranes are yellow solids, and their solutions exhibit an intense blue fluorescence (ΦPL = 85% (3), 89% (5)). According to cyclic voltammetry, reversible reduction occurs at half-wave potentials of E1/2 = −2.05 V (3) and −2.14 V (5; in THF, vs FcH/FcH+). The crystal lattices consist of π-stacked dimers, arranged in herringbone p...
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Steric Shielding vs Structural Constraint in a Boron-Containing Polycyclic Aromatic Hydrocarbon
2016Co-Authors: Valentin M. Hertz, Naoki Ando, Masato Hirai, Michael Bolte, Hans-wolfram Lerner, Shigehiro Yamaguchi, Matthias WagnerAbstract:The highly reactive boron-doped Polycyclic Aromatic Hydrocarbon 8H-8-bromo-8-borabenzo[gh]tetraphene has been synthesized via a multistep sequence encompassing a Peterson olefination, a stilbene-type photocyclization, and an Si/B exchange reaction. The compound was subsequently treated with mesityllithium to give the derivative 3 or with [2,6-bis(propen-2-yl)phenyl]lithium to furnish the intermediate 4. A scandium(III) triflate mediated Friedel–Crafts reaction transformed 4 into the rigid, planarized triarylborane 5. Compounds 3 and 5 are both inert toward air and moisture but are still able to bind fluoride ions, where the affinity of 3 in CHCl3 is higher than that of 5. Both arylboranes are yellow solids, and their solutions exhibit an intense blue fluorescence (ΦPL = 85% (3), 89% (5)). According to cyclic voltammetry, reversible reduction occurs at half-wave potentials of E1/2 = −2.05 V (3) and −2.14 V (5; in THF, vs FcH/FcH+). The crystal lattices consist of π-stacked dimers, arranged in herringbone patterns. Importantly, 3 and 5 share nearly identical properties, despite possessing fundamentally different structures
Ronald G. Harvey - One of the best experts on this subject based on the ideXlab platform.
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Polycyclic Aromatic Hydrocarbon Trans-Dihydrodiol Specificity of four Recombinant Human Dihydrodiol Dehydrogenase Isoforms
Polycyclic Aromatic Compounds, 2000Co-Authors: Michael E. Burczynski, Ronald G. Harvey, Nisha T. Palackal, Trevor M. PenningAbstract:Abstract A major metabolic route of Polycyclic Aromatic Hydrocarbon (PAH) activation proceeds through trans-dihydrodiol intermediates. We have previously shown that a member of the aldo-keto reductase (AKR) superfamily, rat liver dihydrodiol dehydrogenase (DD), catalyzes the NAD(P)+-dependent oxidation of PAH trans-dihydrodiols with the concomitant production of reactive oxygen species and o-semiquinone anion radicals on route to cyto- and geno-toxic o-quinones. The relevance of this pathway in humans, however, is unknown. In these studies, four homogeneous recombinant human homologs of rat liver DD (DD1, DD2, DD4 and DDX) were tested for their ability to oxidize a structural series of PAH trans-dihydrodiols of increasing ring size and methylation. The results indicate that human DDs preferred non-K-region trans-dihydrodiols and that methyl substitution enhanced oxidation rates by human DDs. Thus multiple human AKRs can contribute to the activation of structurally diverse procarcinogenic PAH by catalyzing...
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Generation of reactive oxygen species during the enzymatic oxidation of Polycyclic Aromatic Hydrocarbon trans-dihydrodiols catalyzed by dihydrodiol dehydrogenase.
Chemical research in toxicology, 1996Co-Authors: Trevor M. Penning, S. Tsuyoshi Ohnishi, And Tomoki Ohnishi, Ronald G. HarveyAbstract:Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) catalyzes the oxidation of Polycyclic Aromatic Hydrocarbon (PAH) trans-dihydrodiols (proximate carcinogens) to catechols which rapidly autoxidize to yield o-quinones (Smithgall, T. E., Harvey, R. G., and Penning, T. M. (1988) J. Biol. Chem 263, 1814−1820). Although this pathway suppresses the formation of the PAH anti- and syn-diol epoxides (ultimate carcinogens), the process of autoxidation is anticipated to yield reactive oxygen species (ROS). We now show that the NADP+ dependent oxidation of (±)-trans-1,2-dihydroxy-1,2-dihydronaphthalene (Npdiol) and (±)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (Bpdiol) catalyzed by homogeneous DD is accompanied by the consumption of molecular oxygen and the production of H2O2. With both trans-dihydrodiol substrates, oxygen consumption was stoichiometric with H2O2 production consistent with the reaction: QH2 + O2 = H2O2 + Q, where QH2 is the catechol and Q is the o-quinone. Using Npdiol or Bpdiol as substrates, a burst ...
Trevor M. Penning - One of the best experts on this subject based on the ideXlab platform.
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Polycyclic Aromatic Hydrocarbon Trans-Dihydrodiol Specificity of four Recombinant Human Dihydrodiol Dehydrogenase Isoforms
Polycyclic Aromatic Compounds, 2000Co-Authors: Michael E. Burczynski, Ronald G. Harvey, Nisha T. Palackal, Trevor M. PenningAbstract:Abstract A major metabolic route of Polycyclic Aromatic Hydrocarbon (PAH) activation proceeds through trans-dihydrodiol intermediates. We have previously shown that a member of the aldo-keto reductase (AKR) superfamily, rat liver dihydrodiol dehydrogenase (DD), catalyzes the NAD(P)+-dependent oxidation of PAH trans-dihydrodiols with the concomitant production of reactive oxygen species and o-semiquinone anion radicals on route to cyto- and geno-toxic o-quinones. The relevance of this pathway in humans, however, is unknown. In these studies, four homogeneous recombinant human homologs of rat liver DD (DD1, DD2, DD4 and DDX) were tested for their ability to oxidize a structural series of PAH trans-dihydrodiols of increasing ring size and methylation. The results indicate that human DDs preferred non-K-region trans-dihydrodiols and that methyl substitution enhanced oxidation rates by human DDs. Thus multiple human AKRs can contribute to the activation of structurally diverse procarcinogenic PAH by catalyzing...
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Generation of reactive oxygen species during the enzymatic oxidation of Polycyclic Aromatic Hydrocarbon trans-dihydrodiols catalyzed by dihydrodiol dehydrogenase.
Chemical research in toxicology, 1996Co-Authors: Trevor M. Penning, S. Tsuyoshi Ohnishi, And Tomoki Ohnishi, Ronald G. HarveyAbstract:Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) catalyzes the oxidation of Polycyclic Aromatic Hydrocarbon (PAH) trans-dihydrodiols (proximate carcinogens) to catechols which rapidly autoxidize to yield o-quinones (Smithgall, T. E., Harvey, R. G., and Penning, T. M. (1988) J. Biol. Chem 263, 1814−1820). Although this pathway suppresses the formation of the PAH anti- and syn-diol epoxides (ultimate carcinogens), the process of autoxidation is anticipated to yield reactive oxygen species (ROS). We now show that the NADP+ dependent oxidation of (±)-trans-1,2-dihydroxy-1,2-dihydronaphthalene (Npdiol) and (±)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (Bpdiol) catalyzed by homogeneous DD is accompanied by the consumption of molecular oxygen and the production of H2O2. With both trans-dihydrodiol substrates, oxygen consumption was stoichiometric with H2O2 production consistent with the reaction: QH2 + O2 = H2O2 + Q, where QH2 is the catechol and Q is the o-quinone. Using Npdiol or Bpdiol as substrates, a burst ...
Sun Kwok - One of the best experts on this subject based on the ideXlab platform.
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a theoretical study on the vibrational spectra of Polycyclic Aromatic Hydrocarbon molecules with aliphatic sidegroups
The Astrophysical Journal, 2015Co-Authors: Seyedabdolreza Sadjadi, Yong Zhang, Sun KwokAbstract:The role of aliphatic side groups in the formation of astronomical unidentified infrared emission (UIE) features is investigated by applying the density functional theory to a series of molecules with mixed aliphatic-Aromatic structures. The effects of introducing various aliphatic groups to a fixed Polycyclic Aromatic Hydrocarbon (PAH) core (ovalene) are studied. Simulated spectra for each molecule are produced by applying a Drude profile at T = 500 K while the molecule is kept at its electronic ground state. The vibrational normal modes are classified using a semi-quantitative method. This allows us to separate the Aromatic and aliphatic vibrations, and therefore provides clues to what types of vibrations are responsible for the emissions bands at different wavelengths. We find that many of the UIE bands are not pure Aromatic vibrational bands but may represent coupled vibrational modes. The effects of aliphatic groups on the formation of the 8 μm plateau are quantitatively determined. The vibrational motions of methyl (–CH3) and methylene (–CH2 –) groups can cause the merging of the vibrational bands of the parent PAH and the forming of broad features. These results suggest that aliphatic structures can play an important role in the UIE phenomenon.
Valentin M Hertz - One of the best experts on this subject based on the ideXlab platform.
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steric shielding vs structural constraint in a boron containing Polycyclic Aromatic Hydrocarbon
Organometallics, 2017Co-Authors: Valentin M Hertz, Naoki Ando, Masato Hirai, Michael Bolte, Hans-wolfram Lerner, Shigehiro Yamaguchi, Matthias WagnerAbstract:The highly reactive boron-doped Polycyclic Aromatic Hydrocarbon 8H-8-bromo-8-borabenzo[gh]tetraphene has been synthesized via a multistep sequence encompassing a Peterson olefination, a stilbene-type photocyclization, and an Si/B exchange reaction. The compound was subsequently treated with mesityllithium to give the derivative 3 or with [2,6-bis(propen-2-yl)phenyl]lithium to furnish the intermediate 4. A scandium(III) triflate mediated Friedel–Crafts reaction transformed 4 into the rigid, planarized triarylborane 5. Compounds 3 and 5 are both inert toward air and moisture but are still able to bind fluoride ions, where the affinity of 3 in CHCl3 is higher than that of 5. Both arylboranes are yellow solids, and their solutions exhibit an intense blue fluorescence (ΦPL = 85% (3), 89% (5)). According to cyclic voltammetry, reversible reduction occurs at half-wave potentials of E1/2 = −2.05 V (3) and −2.14 V (5; in THF, vs FcH/FcH+). The crystal lattices consist of π-stacked dimers, arranged in herringbone p...