Electronic and Raman spectroscopic properties of oxo-bridged dinuclear iron centers in proteins and model compounds

Sanders-Loehr, Joann; Wheeler, William D.; Shiemke, Andrew K.; Averill, Bruce A.; Loehr, Thomas M.

doi:10.1021/ja00203a003

Cited by 207 publications

(209 citation statements)

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“…Methane monooxygenase also differs from the R2 protein of ribonucleotide reductase by having a hydroxo species as the bridging oxygen instead of a ,u-0x0 group. The absorbance in the 300-400 nm region of ribonucleotide reductase has been assigned to an 0x0 -+ Fe3' charge transfer band [27] which is shifted to lower wavelengths when the oxygen is protonated [28], accounting for the lack of electronic absorption above 300 nm in methane monooxygenase. An additional feature of both the methane monooxygenase and ribonucleotide reductase active sites is the presence of a hydrophobic cavity formed adjacent to the iron center by a series of conserved residues within the four-helical bundle (Fig.…”

Section: Introductionmentioning

confidence: 99%

The active site of the cyanide‐resistant oxidase from plant mitochondria contains a binuclear iron center

1995

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The cyanide-resistant, alternative oxidase of plant mitochondria catalyzes the four-electron reduction of oxygen to water, but the nature of the catalytic center associated with this oxidase has yet to be elucidated. We have identified conserved amino acids, including two copies of the iron-binding motif GIu-X-X-His, in the carboxy-terminal hydrophilic domain of the alternative oxidase that suggest the presence of a hydroxo-bridged binuclear iron center, analogous to that found in the enzyme methane monooxygenase. Using the known three-dimensional structures of other binuclear iron proteins, we have developed a structural model for the proposed catalytic site of the alternative oxidase based on these amino acid sequence similarities.

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Section: Introductionmentioning

confidence: 99%

The active site of the cyanide‐resistant oxidase from plant mitochondria contains a binuclear iron center

1995

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“…S1)]. As an alternative, the NRVS spectrum of the Fe(III) 2 (Table S1) (34). Due to the difference in energy of the major NRVS features of the Fe(III) 2 precursor relative to the high-valent Fe(IV) 2 and Fe(III)Fe(IV) species, samples that had some decay to the Fe(III) 2 species (due to accidental warming above −80°C in transfer) were excluded during data collection.…”

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confidence: 99%

Nuclear resonance vibrational spectroscopic and computational study of high-valent diiron complexes relevant to enzyme intermediates

Park

Bell

Liu

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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High-valent intermediates of binuclear nonheme iron enzymes are structurally unknown despite their importance for understanding enzyme reactivity. Nuclear resonance vibrational spectroscopy combined with density functional theory calculations has been applied to structurally well-characterized high-valent mono-and di-oxo bridged binuclear Fe model complexes. Low-frequency vibrational modes of these high-valent diiron complexes involving Fe motion have been observed and assigned. These are independent of Fe oxidation state and show a strong dependence on spin state. It is important to note that they are sensitive to the nature of the Fe 2 core bridges and provide the basis for interpreting parallel nuclear resonance vibrational spectroscopy data on the highvalent oxo intermediates in the binuclear nonheme iron enzymes.iron-oxo cores | Fe enzymes C lass Ia ribonucleotide reductase (RR) (1) and soluble methane monooxygenase (sMMO) (2) are members of the class of binuclear nonheme iron enzymes. These have intrigued researchers due to their significance in the development of anticancer drugs (RR) (3) and biofuel catalysts (sMMO) (4) and their varied reactivities using a conserved 2 His/4 carboxylate ligand set. These enzymes use a biFe active site to activate O 2 for hydrogen atom abstraction and hydroxylation via key high-valent intermediates called X (5, 6) and Q (7, 8) in RR and sMMO, respectively.

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“…100 nm (eV) suggesting that it is not associated with the π-conjugated ring. Fe-O-Fe bridges have been reported to exhibit UV/vis absorbances at 360-380 nm which have been attributed to charge transfer states [15,[22][23][24][25]. Although they are not evident in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The complexity of the spectra makes it difficult to identify any features uniquely attributable to the dimer and consequently the Fe-O-Fe bridge. While the asymmetric stretch of bridged porphyrin dimers has been reported to lie at ≈ 850 cm −1 , the symmetric stretch, which should be Raman active, has been reported to lie at ≈ 450 cm −1 [14,15,[25][26][27][28]. In the spectra of Fig.…”

Section: Resultsmentioning

confidence: 99%

Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

Dziedzic-Kocurek

Byrne²,

Swiderski

et al. 2009

Acta Phys. Pol. A

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The commercial protoporphyrin IX, iron-ferriprotoporphyrin IX-chloride and synthesized iron porphyrin µ-oxo-dimers were examined by UV/vis absorption and fluorescence, Fourier transformed infrared spectroscopy, resonance Raman, X-ray absorption, Mössbauer spectroscopy and SQUID. The evidence of Fe-O-Fe antiferromagnetic coupling concluded from SQUID and Mössbauer in the case of samples containing dimerized forms confirmed the presence of the oxo-bridges. In this paper the results of UV/vis, fluorescence, Fourier transform infrared FTIR and Raman spectroscopies are reported and discussed. The study is based on the comparison of the free-base protoporphyrin IX, Fe-PPIX-Cl and the synthesized dimerized specimen. The vibrational modes in two energy regions i.e. 330-650 cm −1 and 750-900 cm −1 , reportedly characteristic of the existence of Fe-O-Fe bridges, are discussed. A significant photoluminescence emission, strongly Stokes shifted from the Soret band, absent in the protoporphyrin IX and the iron-ferriprotoporphyrin IX-chloride, is observed. The strong Stokes shift and the mismatch of the excitation spectrum to the Soret band suggest that is does not have origin in the de-excitation of the porphyrin moiety and that it could have origin in an Fe-O-Fe charge transfer state.

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Electronic and Raman spectroscopic properties of oxo-bridged dinuclear iron centers in proteins and model compounds

Cited by 207 publications

References 1 publication

The active site of the cyanide‐resistant oxidase from plant mitochondria contains a binuclear iron center

The active site of the cyanide‐resistant oxidase from plant mitochondria contains a binuclear iron center

Nuclear resonance vibrational spectroscopic and computational study of high-valent diiron complexes relevant to enzyme intermediates

Spectroscopic Study of the Dimerization Process οf Iron Protoporphyrin IX

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