Following the heme paradigm, it is often proposed that dioxygen activation by nonheme monoiron enzymes involves an iron(IV)=oxo intermediate responsible for substrate oxidation step. Such a transient species has now been obtained from synthetic complex with macrocyclic ligand and characterized spectroscopically. Its high-resolution crystal structure reveals iron-oxygen bond length of 1.646(3) angstroms, demonstrating terminal unit can exist in nonporphyrin environment lending credence to...

Nonheme oxoiron(IV) complexes of two pentadentate ligands, N4Py (N,N-bis(2-pyridylmethyl)-bis(2-pyridyl)methylamine) and Bn-tpen (N-benzyl-N,N',N'-tris(2-pyridylmethyl)-1,2-diaminoethane), have been generated found to spectroscopic properties similar the closely related tetradentate TPA (tris(2-pyridylmethyl)amine) complex reported earlier. However, unlike complex, a considerable lifetime at room temperature. This greater thermal stability has allowed hydroxylation alkanes with C−H bonds as...

A new paradigm for oxygen activation is required enzymes such as methane monooxygenase (MMO), which catalysis depends on a nonheme diiron center instead of the more familiar Fe-porphyrin cofactor. On basis precedents from synthetic complexes, high-valent Fe 2 (μ-O) diamond core has been proposed key oxidizing species MMO and other ribonucleotide reductase fatty acid desaturase. The presence single short Fe-O bond (1.77 angstroms) per atom an Fe-Fe distance 2.46 angstroms in reaction...

Iron(V)-oxo species have been proposed as key reactive intermediates in the catalysis of oxygen-activating enzymes and synthetic catalysts. Here, we report synthesis [Fe(TAML)(O)]- nearly quantitative yield, where TAML is a macrocyclic tetraamide ligand. Mass spectrometry, Mössbauer, electron paramagnetic resonance, x-ray absorption spectroscopies, well reactivity studies density functional theory calculations show that this long-lived (hours at -60 degrees C) intermediate spin S = 1/2...

A combination of techniques (Mössbauer and X-ray absorption spectroscopy, H218O exchange experiments, DFT calculations) has shown that the reaction [Fe(H2O)6]2+ with ozone generates [(H2O)5FeIVO]2+ (see calculated structure). The oxidation selected substrates yields unique products are different from those generated in Fenton or derived HO. radicals. Supporting information for this article is available on WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z502686_s.pdf author. Please...

The transcription factor FNR ( f umarate n itrate r eduction) requires the presence of an iron-sulfur (Fe-S) cluster for its function as a global regulator in Escherichia coli when oxygen becomes scarce. To define oxidation state and type Fe-S present active form FNR, we have studied anaerobically purified with Mössbauer spectroscopy. Our data showed that this contained [4Fe-4S] 2+ (δ = 0.45 mm/s; Δ E Q 1.22 mm/s) was rapidly destroyed on exposure to air. Under these conditions, yellow–green...

The reaction of [Fe II (tris(2-pyridylmethyl)amine, TPA)(NCCH 3 ) 2 ] 2+ with 1 equiv. peracetic acid in CH CN at −40°C results the nearly quantitative formation a pale green intermediate λ max 724 nm (ɛ ≈ 300 M −1 ⋅cm formulated as IV (O)(TPA)] by combination spectroscopic techniques. Its electrospray mass spectrum shows prominent feature m / z 461, corresponding to (O)(TPA)(ClO 4 )] + ion. Mössbauer spectra recorded zero field reveal doublet Δ E Q = 0.92(2) mm/s and δ 0.01(2) mm/s;...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA transient intermediate of the methane monooxygenase catalytic cycle containing an FeIVFeIV clusterSang Kyu Lee, Brian G. Fox, Wayne A. Froland, John D. Lipscomb, and Eckard MunckCite this: J. Am. Chem. Soc. 1993, 115, 14, 6450–6451Publication Date (Print):July 1, 1993Publication History Published online1 May 2002Published inissue 1 July 1993https://pubs.acs.org/doi/10.1021/ja00067a086https://doi.org/10.1021/ja00067a086research-articleACS...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and comparative reactivity electronic structural features of [MFe3S4]z+ cubane-type clusters (M = iron, cobalt, nickel)Jian Zhou, Michael J. Scott, Zhengguo Hu, Gang Peng, E. Munck, R. H. HolmCite this: Am. Chem. Soc. 1992, 114, 27, 10843–10854Publication Date (Print):December 1, 1992Publication History Published online1 May 2002Published inissue 1 December...

High versus low: The high-yield generation of a synthetic high-spin oxoiron(IV) complex, [Fe(IV)(O)(TMG(3)tren)](2+) (see picture, TMG(3)tren = 1,1,1-tris{2-[N2-(1,1,3,3-tetramethylguanidino)]ethyl}amine), has been achieved by using the very bulky tetradentate ligand, in order to both sterically protect moiety and enforce trigonal bipyramidal geometry at iron center, for which an S 2 ground state is favored.

Thiolate-ligated oxoiron(IV) centers are postulated to be the key oxidants in catalytic cycles of oxygen-activating cytochrome P450 and related enzymes. Despite considerable synthetic efforts, chemists have not succeeded preparing an appropriate model complex. Here we report synthesis spectroscopic characterization [FeIV(O)(TMCS)]+ where TMCS is a pentadentate ligand that provides square pyramidal N4(SR)apical, SR thiolate, environment about iron center, which similar P450. The rigidity...

We have purified the Rieske iron-sulfur protein from Thermus thermophilus.Chemical analyses show that contains iron, labile sulfide, and cysteine in equimolar concentrations, four of each for M, -20,000.The oxidized reduced form been characterized by optical, EPR, CD, magnetic CD Mossbauer spectroscopies.Our data suggest presence a unique center.Mossbauer studies demonstrate unambiguously clusters with [2Fe-2S] cores.The iron data, taken together, has two clusters.This is supported...

Mononuclear iron(III) species with end-on and side-on peroxide have been proposed or identified in the catalytic cycles of antitumor drug bleomycin a variety enzymes, such as cytochrome P450 Rieske dioxygenases. Only recently biomimetic analogues reactive generated characterized at low temperatures. We report synthesis characterization series iron(II) complexes pentadentate N5 ligands that react H2O2 to generate transient low-spin FeIII−OOH intermediates. These intermediates centers...

A gene encoding stearoyl-acyl carrier protein delta 9 desaturase (EC 1.14.99.6) from castor was expressed in Escherichia coli. The purified catalytically active enzyme contained four atoms of iron per homodimer. studied two oxidation states with Mössbauer spectroscopy applied fields up to 6.0 T. These studies show conclusively that the oxidized contains (identical) clusters consisting a pair antiferromagnetically coupled (J > 60 cm-1, H = JS1.S2) Fe3+ sites. diferric cluster exhibited...

Elemental analyses, Mössbauer, and EPR data are reported to show that endonuclease III of Escherichia coli is an iron-sulfur protein. Mössbauer spectra protein freshly prepared from E. grown on 57Fe-enriched medium demonstrate the native enzyme contains a single 4Fe-4S cluster in 2+ oxidation state, with net spin zero. Upon treatment ferricyanide, fraction (less than 25%) clusters oxidized into state which yields spectrum near g = 2.01 typical 3Fe-4S cluster. The magnetic field dependence...

We have studied the high and low potential ironsulfur centers of an Azotobacter vinelandii ferredoxin with Mossbauer spectroscopy.The data suggest that cluster is Fe4Sc type center (Eo = -420 mV) represents a novel cluster.The oxidized which exhibits isotropic EPR signal at g 2.01 has least 2 distinct iron sites identical quadrupole splittings, AEQ 0.63 mm/s, isomeric shifts, B 0.27 suggesting spin ferric ions tetrahedral sulfur ligation.The two display dras-.tically different magnetic...

The gene encoding the alkane ω-hydroxylase (AlkB; EC 1.14.15.3 ) from Pseudomonas oleovorans was expressed in Escherichia coli . integral-membrane protein purified as nearly homogeneous vesicles by differential ultracentrifugation and HPLC cation exchange chromatography without detergent solubilization normally required for membrane proteins. Purified AlkB had specific activity of up to 5 units/mg octane-dependent NADPH consumption. Mössbauer studies showed that it contains an...

Mössbauer spectra of [LFeIIX]0 (L = β-diketiminate; X Cl-, CH3-, NHTol-, NHtBu-), 1.X, were recorded between 4.2 and 200 K in applied magnetic fields up to 8.0 T. A spin Hamiltonian analysis these data revealed a S 2 system with uniaxial magnetization properties, arising from quasi-degenerate MS ±2 doublet that is separated the next sublevels by very large zero-field splittings (3|D| > 150 cm-1). The ground levels give rise positive hyperfine unprecedented magnitudes, Bint +82, +78, +72, +62...

The tetrameric form of a Desulfovibrio gigas ferredoxin, named Fd 11, mediates electron transfer between cytochrome c3 and sulfite reductase.We have studied two stable oxidation states this protein with Mossbauer spectroscopy paramagnetic resonance.We found 3 iron atoms/monomer spin concentration 0.9 spins/monomer for the oxidized protein.Taken together, EPR data demonstrate conclusively presence spin-coupled structure containing atoms labile sulfur.The show also that metal center is...

Mossbauer and EPR studies of a highly active hydroxylase component methane monooxygenase isolated from Methyloeinue trichoeporium OB3b are reported.The spectra the oxidized (as isolated) show iron in diamagnetic cluster containing an even number FeS+ sites.The parameters consistent with antiferromagnetically coupled binuclear similar to those hemerythrin purple acid phosphatases.Upon partial reduction hydroxylase, S = $5 spectrum g values at 1.94,1.86,and 1.75 (gaV 1.85) is observed.Such...

We have studied the Fe protein (Av2) of Axotobacter uinelandii nitrogenase system with Miissbauer and EPR spectroscopies magnetic susceptometry.In oxidized state exhibits Mossbauer spectra typical diamagnetic [4Fe-4SI2+ clusters.Addition Mg*ATP or Mg*ADP causes a pronounced decline in quadrupole splitting protein.Our studies show that reduced Av2 native is heterogeneous.Ap- proximately half molecules contain [4Fe-4SI1+ cluster electronic spin S = 1h Yz.The former yields characteristic g 1.94...