The Experts below are selected from a list of 279714 Experts worldwide ranked by ideXlab platform
Adam T. Fiedler - One of the best experts on this subject based on the ideXlab platform.
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A Synthetic Model of the Putative Fe(II)-Iminobenzosemiquinonate Intermediate in the Catalytic Cycle of o-Aminophenol Dioxygenases
2012Co-Authors: Michael M. Bittner, Sergey V. Lindeman, Adam T. FiedlerAbstract:The oxidative ring cleavage of aromatic substrates by nonheme Fe dioxygenases is thought to involve formation of a ferrous–(substrate radical) intermediate. Here we describe the synthesis of the trigonal-bipyramdial complex Fe(Ph2Tp)(ISQtBu) (2), the first Synthetic example of an iron(II) center bound to an iminobenzosemiquinonate (ISQ) radical. The unique electronic structure of this S = 3/2 complex and its one-electron oxidized derivative ([3]+) have been established on the basis of crystallographic, spectroscopic, and computational analyses. These findings further demonstrate the viability of Fe2+–ISQ intermediates in the catalytic cycles of o-aminophenol dioxygenases
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insights into the p to q conversion in the catalytic cycle of methane monooxygenase from a Synthetic Model system
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Genqiang Xue, Adam T. Fiedler, Marlene Martinho, Eckard Munck, Lawrence QueAbstract:For the catalytic cycle of soluble methane monooxygenase (sMMO), it has been proposed that cleavage of the O–O bond in the (μ-peroxo)diiron(III) intermediate P gives rise to the diiron(IV) intermediate Q with an Fe2(μ–O)2 diamond core, which oxidizes methane to methanol. As a Model for this conversion, (μ–oxo) diiron(III) complex 1 ([FeIII2(μ–O)(μ–O2H3)(L)2]3+, L = tris(3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) has been treated consecutively with one eq of H2O2 and one eq of HClO4 to form 3 ([FeIV2(μ–O)2(L)2]4+). In the course of this reaction a new species, 2, can be observed before the protonation step; 2 gives rise to a cationic peak cluster by ESI-MS at m/z 1,399, corresponding to the {[Fe2O3L2H](OTf)2}+ ion in which 1 oxygen atom derives from 1 and the other two originate from H2O2. Mossbauer studies of 2 reveal the presence of two distinct, exchange coupled iron(IV) centers, and EXAFS fits indicate a short Fe–O bond at 1.66 Å and an Fe–Fe distance of 3.32 Å. Taken together, the spectroscopic data point to an HO-FeIV-O-FeIV = O core for 2. Protonation of 2 results in the loss of H2O and the formation of 3. Isotope labeling experiments show that the [FeIV2(μ–O)2] core of 3 can incorporate both oxygen atoms from H2O2. The reactions described here serve as the only biomimetic precedent for the conversion of intermediates P to Q in the sMMO reaction cycle and shed light on how a peroxodiiron(III) unit can transform into an [FeIV2(μ–O)2] core.
James P. Collman - One of the best experts on this subject based on the ideXlab platform.
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intermediates involved in the two electron reduction of no to n2o by a functional Synthetic Model of heme containing bacterial no reductase
Journal of the American Chemical Society, 2008Co-Authors: James P. Collman, Abhishek Dey, Ying Yang, Richard A Decreau, Takehiro Ohta, Edward I SolomonAbstract:Reaction of a functional biferrous heme/nonheme Model complex at low temperature leads to the formation of a distal nonheme nitrosyl followed by a trans heme nonheme bis-nitrosyl intermediate. The EPR and Raman data on this intermediate indicate that the two nitrosyl centers are close. This complex gives off N2O and provides support for the trans mechanism proposed for NOR enzymes.
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Efficient Synthesis of Trisimidazole and Glutaric Acid Bearing Porphyrins: Ligands for Active-Site Models of Bacterial Nitric Oxide Reductase
Organic letters, 2006Co-Authors: James P. Collman, Yi-long Yan, Jianping Lei, Peter H. DinolfoAbstract:Ligands (1) for active-site Models of bacterial nitric oxide reductase (NOR) have been efficiently synthesized. These compounds (1) feature three imidazolyl moieties and one carboxylic acid residue at the FeB site, which represent the closest available Synthetic Model ligands of NOR active center. The stereo conformations of these ligands are established on the basis of steric effects and 1H NMR chemical shifts under the ring current effect of the porphyrin.
Lawrence Que - One of the best experts on this subject based on the ideXlab platform.
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insights into the p to q conversion in the catalytic cycle of methane monooxygenase from a Synthetic Model system
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Genqiang Xue, Adam T. Fiedler, Marlene Martinho, Eckard Munck, Lawrence QueAbstract:For the catalytic cycle of soluble methane monooxygenase (sMMO), it has been proposed that cleavage of the O–O bond in the (μ-peroxo)diiron(III) intermediate P gives rise to the diiron(IV) intermediate Q with an Fe2(μ–O)2 diamond core, which oxidizes methane to methanol. As a Model for this conversion, (μ–oxo) diiron(III) complex 1 ([FeIII2(μ–O)(μ–O2H3)(L)2]3+, L = tris(3,5-dimethyl-4-methoxypyridyl-2-methyl)amine) has been treated consecutively with one eq of H2O2 and one eq of HClO4 to form 3 ([FeIV2(μ–O)2(L)2]4+). In the course of this reaction a new species, 2, can be observed before the protonation step; 2 gives rise to a cationic peak cluster by ESI-MS at m/z 1,399, corresponding to the {[Fe2O3L2H](OTf)2}+ ion in which 1 oxygen atom derives from 1 and the other two originate from H2O2. Mossbauer studies of 2 reveal the presence of two distinct, exchange coupled iron(IV) centers, and EXAFS fits indicate a short Fe–O bond at 1.66 Å and an Fe–Fe distance of 3.32 Å. Taken together, the spectroscopic data point to an HO-FeIV-O-FeIV = O core for 2. Protonation of 2 results in the loss of H2O and the formation of 3. Isotope labeling experiments show that the [FeIV2(μ–O)2] core of 3 can incorporate both oxygen atoms from H2O2. The reactions described here serve as the only biomimetic precedent for the conversion of intermediates P to Q in the sMMO reaction cycle and shed light on how a peroxodiiron(III) unit can transform into an [FeIV2(μ–O)2] core.
Nicolai Lehnert - One of the best experts on this subject based on the ideXlab platform.
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Synthetic Model complex of the key intermediate in cytochrome p450 nitric oxide reductase
Inorganic Chemistry, 2019Co-Authors: Ashley B Mcquarters, Elizabeth J Blaesi, Jeff W Kampf, Ercan E Alp, Jiyong Zhao, Carsten Krebs, Nicolai LehnertAbstract:Fungal denitrification plays a crucial role in the nitrogen cycle and contributes to the total N2O emission from agricultural soils. Here, cytochrome P450 NO reductase (P450nor) reduces two NO to N2O using a single heme site. Despite much research, the exact nature of the critical “Intermediate I” responsible for the key N–N coupling step in P450nor is unknown. This species likely corresponds to a Fe-NHOH-type intermediate with an unknown electronic structure. Here we report a new strategy to generate a Model system for this intermediate, starting from the iron(III) methylhydroxylamide complex [Fe(3,5-Me-BAFP)(NHOMe)] (1), which was fully characterized by 1H NMR, UV–vis, electron paramagnetic resonance, and vibrational spectroscopy (rRaman and NRVS). Our data show that 1 is a high-spin ferric complex with an N-bound hydroxylamide ligand that is strongly coordinated (Fe–N distance, 1.918 A; Fe-NHOMe stretch, 558 cm–1). Simple one-electron oxidation of 1 at −80 °C then cleanly generates the first Model syst...
Peter H. Dinolfo - One of the best experts on this subject based on the ideXlab platform.
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Efficient Synthesis of Trisimidazole and Glutaric Acid Bearing Porphyrins: Ligands for Active-Site Models of Bacterial Nitric Oxide Reductase
Organic letters, 2006Co-Authors: James P. Collman, Yi-long Yan, Jianping Lei, Peter H. DinolfoAbstract:Ligands (1) for active-site Models of bacterial nitric oxide reductase (NOR) have been efficiently synthesized. These compounds (1) feature three imidazolyl moieties and one carboxylic acid residue at the FeB site, which represent the closest available Synthetic Model ligands of NOR active center. The stereo conformations of these ligands are established on the basis of steric effects and 1H NMR chemical shifts under the ring current effect of the porphyrin.
