Multi-frequency and high-field EPR study of manganese(III) protoporphyrin IX reconstituted myoglobin with an S= 2 integer electron spin

Horitani, Masaki; Yashiro, Haruhiko; Hagiwara, Masayuki; Hori, Hiroshi

doi:10.1016/j.jinorgbio.2007.11.015

Cited by 18 publications

(11 citation statements)

References 26 publications

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“…Figures a,b show electron paramagnetic resonance (EPR) spectra of the resting state of rMb in perpendicular- and parallel-mode measurements, respectively, to assign the electronic states of the intermediate. The integer spin ( S = 2) is expected for the resting state according to a previous report of Mn-substituted Mb . In the case of the Mn III species of rMb, the broad signals are only observed in the spectrum using the perpendicular mode, whereas the parallel mode obviously demonstrates characteristic EPR signals, which are typical for the integer spin species.…”

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confidence: 62%

“…In nMb, the reduction of compound I by amino acid residues such as tyrosine is extremely fast (≪1 ms) . Similarly, Mbs reconstituted with iron porphycene and manganese protoporphyrin IX do not generate detectable compound I-like species and lose the opportunity to abstract a hydrogen atom from an external substrate. ,,, Thus, detection of the desired intermediate is important to determine the possibility of hydroxylation of external substrates in the Mb-based system. Although the stable intermediate is generally less reactive from the viewpoint of C–H bond activation, the basicity of the Mn V -oxo species appears to be high to compensate for the disadvantage of the redox potential. , In the case of the present system, longer half-life, which is equivalent with the less nonproductive decay of the Mn V -oxo species, and higher TON are observed at higher pH, whereas the pH value does not affect the reactivity of the Mn V -oxo species (Figure S7 and Table S3).…”

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confidence: 99%

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Manganese(V) Porphycene Complex Responsible for Inert C–H Bond Hydroxylation in a Myoglobin Matrix

et al. 2017

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A mechanistic study of HO-dependent C-H bond hydroxylation by myoglobin reconstituted with a manganese porphycene was carried out. The X-ray crystal structure of the reconstituted protein obtained at 1.5 Å resolution reveals tight incorporation of the complex into the myoglobin matrix at pH 8.5, the optimized pH value for the highest turnover number of hydroxylation of ethylbenzene. The protein generates a spectroscopically detectable two-electron oxidative intermediate in a reaction with peracid, which has a half-life up to 38 s at 10 °C. Electron paramagnetic resonance spectra of the intermediate with perpendicular and parallel modes are silent, indicating formation of a low-spin Mn-oxo species. In addition, the Mn-oxo species is capable of promoting the hydroxylation of sodium 4-ethylbenzenesulfonate under single turnover conditions with an apparent second-order rate constant of 2.0 M s at 25 °C. Furthermore, the higher bond dissociation enthalpy of the substrate decreases the rate constant, in support of the proposal that the H-abstraction is one of the rate-limiting steps. The present engineered myoglobin serves as an artificial metalloenzyme for inert C-H bond activation via a high-valent metal species similar to the species employed by native monooxygenases such as cytochrome P450.

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confidence: 62%

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confidence: 99%

Manganese(V) Porphycene Complex Responsible for Inert C–H Bond Hydroxylation in a Myoglobin Matrix

et al. 2017

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“…ZFS was reported to be about D E 3.4-5.0 cm À1 for Mn 3+ in tetragonal complexes, while the electron Zeeman interaction in X-band EPR magnetic fields is an order of magnitude smaller, 0.2-0.3 cm À1 , and the Mn hyperfine term is B0.1 cm À1 . [50][51][52] The case where S = 2 in strong ZFS has been considered in detail, and the expressions for the energy levels have been derived to the second order in perturbation theory. Strong ZFS splits the spin levels into two non-Kramer (NK) doublets, nominally M S = AE1 and M S = AE2 states, and a singlet M S = 0 state.…”

Section: Discussionmentioning

confidence: 99%

Manganese-Schiff base complexes as catalysts for water photolysis

González-Riopedre

Fernández-García

Noya

et al. 2011

Phys. Chem. Chem. Phys.

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Four manganese(III)-Schiff base complexes (1-4) of formula [MnL n (H 2 O) 2 ] 2 (ClO 4 ) 2 ÁmH 2 O (n = 1-4; m = 0, 1) have been prepared. The multidentate H 2 L n Schiff base ligands consist of 3R,5R-substituted N,N 0 -bis(salicylidene)-1,2-diimino-2,2-dimethylethane, where R = OEt, OMe, Br or Cl. The complexes have been thoroughly characterized by elemental analysis, mass spectrometry, magnetic susceptibility measurements, IR, UV, paramagnetic 1 H NMR and EPR spectroscopies. Other properties, including redox studies and molar conductivity measurements, have also been assessed. The crystal structure of 1 was solved by X-ray diffraction, which revealed the dimeric nature of the compound through m-aqua bridges. The ability of these complexes to split water has been studied by water photolysis experiments, with the oxygen evolution measured in aqueous media in the presence of a hydrogen acceptor (p-benzoquinone), the reduction of which was followed by UV-spectroscopy. The discussion of the photolytic behaviour includes advances in the knowledge of the structural motifs and the chemical activity of this type of complex, as revealed by the development of several characterization techniques in the last decade. Parallel-mode Mn III EPR shows that complexes 1-4 not only mimic reactivity but also share some structural characteristics from partially assembled natural OEC clusters.

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“…Early studies of SH parameters of Mn(III) ions in porphyrinic and related complexes have been reviewed in [11], whereas more recent studies include, e.g. [12][13][14].…”

Section: Introductionmentioning

confidence: 99%

EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

Tadyszak

Rudowicz

2017

Acta Phys. Pol. A

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The electron magnetic resonance data on high-spin (S = 2) manganese(III) 3d 4 ion in tetraphenylporphyrinato chloride complex (MnTPPCl) obtained by high-frequency techniques are reanalysed. Preliminary results of semiempirical modeling of the spin Hamiltonian parameters for Mn(III) in MnTPPCl are presented. The microscopic spin Hamiltonian approach is utilized to predict the zero-field splitting and the Zeeman electronic parameters. It is found that for Mn(III) ions in MnTPPCl matching the experimental spin Hamiltonian parameters and the theoretical ones based on the ligand-field energy levels (∆i) within the 5 D multiplet only may not be suitable for this system. Contributions due to the levels arising from the higher-lying 3 H multiplet need to be taken into account in order to determine the reasonable values of microscopic parameters describing Mn(III) ions in MnTPPCl.

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Multi-frequency and high-field EPR study of manganese(III) protoporphyrin IX reconstituted myoglobin with an S= 2 integer electron spin

Cited by 18 publications

References 26 publications

Manganese(V) Porphycene Complex Responsible for Inert C–H Bond Hydroxylation in a Myoglobin Matrix

Manganese(V) Porphycene Complex Responsible for Inert C–H Bond Hydroxylation in a Myoglobin Matrix

Manganese-Schiff base complexes as catalysts for water photolysis

EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

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