The new biomimetic ligands N4Py2Ph (1) and N4Py2Ph,amide (2) were synthesized yield the iron(II) complexes [FeII(N4Py2Ph)(NCCH3)](BF4)2 (3) [FeII(N4Py2Ph,amide)](BF4)2 (5). Controlled orientation of Ph substituents in 3 leads to facile triplet spin reactivity for a putative FeIV(O) intermediate, resulting rapid arene hydroxylation. Addition peripheral amide substituent within hydrogen-bond distance iron first coordination sphere stabilization high-spin FeIIIOOR species which decays without...

A new alkylthiolate-ligated nonheme iron complex, FeII(BNPAMe2S)Br (1), is reported. Reaction of 1 with O2 at −40 °C, or reaction the ferric form O2•– −80 gives a rare iron(III)-superoxide intermediate, [FeIII(O2)(BNPAMe2S)]+ (2), characterized by UV–vis, 57Fe Mössbauer, ATR-FTIR, EPR, and CSIMS. Metastable 2 then converts to an S-oxygenated FeII(sulfinate) product via sequential O atom transfer mechanism involving iron-sulfenate intermediate. These results provide evidence for feasibility...

Non-heme diiron clusters occur in a number of enzymes (e.g., ribonucleotide reductase, methane monooxygenase, and Delta9-stearoyl-ACP desaturase) that activate O2 for chemically difficult oxidation reactions. In each case, kinetically labile peroxo intermediate is believed to form when reacts with the diferrous enzyme, followed by O-O bond cleavage formation high-valent iron intermediates [formally Fe(IV)] are thought be reactive oxidants. Greater kinetic stability peroxodiiron(III) protein...

Ferritins are ubiquitous proteins that concentrate, store, and detoxify intracellular iron through oxidation of Fe2+ (ferroxidation), followed by translocation hydrolysis to form a large inorganic mineral core. A series mutagenesis, kinetics, spectroscopic studies ferritin led the proposal oxidation/translocation path involves diiron protein site. Recent stopped-flow absorption rapid freeze−quench Mössbauer have identified single peroxodiferric species as initial transient intermediate...

To examine the roles of proximal thiolate iron ligand, C357H mutant P450cam (CYP101) was characterized by resonance Raman, UV, circular dichroism, and activity measurements. The must be reconstituted with hemin for to observed. enzyme is a mixture high low spin species. Low temperature (10 °C), concentration (1 μM), camphor mM), 5−50 mM buffer concentrations increase ratio, but under no conditions examined protein more than 60% spin. has poorer Km (23 vs 2 μM) Kd putidaredoxin (50 20...

In Bacillus subtilis, NsrR is required for the upregulation of ResDE-dependent genes in presence nitric oxide (NO). was shown to bind promoters these and inhibit their transcription vitro. NO relieves this inhibition by an unknown mechanism. Here, we use spectroscopic techniques (UV-vis, resonance Raman, EPR) show that anaerobically isolated from B. subtilis contains a [4Fe-4S](2+) cluster, which reacts with form dinitrosyl iron complexes. This method sensing analogous FNR protein...

The rebound mechanism for alkane hydroxylation was invoked over 40 years ago to help explain reactivity patterns in cytochrome P450, and subsequently has been used provide insight into a range of biological synthetic systems. Efforts model the reaction system have unsuccessful, part because challenge preparing suitable metal-hydroxide complex at correct oxidation level. Herein we report synthesis such complex. this species with series substituted radicals allows direct interrogation process,...

High-valent ferryl species (e.g., (Por)Fe

The synthesis and characterization of a Co(II) dithiolato complex Co(Me3TACN)(S2SiMe2) (1) are reported. Reaction 1 with O2 generates rare thiolate-ligated cobalt–superoxo species Co(O2)(Me3TACN)(S2SiMe2) (2) that was characterized spectroscopically structurally by resonance Raman, EPR, X-ray absorption spectroscopies as well density functional theory. Metal–superoxo proposed to S-oxygenate metal-bound thiolate donors in nonheme thiol dioxygenases, but 2 does not lead S-oxygenation the...

Conversion of heme to verdoheme by oxygenase-1 (HO-1) is thought involve α-meso-hydroxylation and elimination the meso-carbon as CO, a reaction supported both H2O2 NADPH-cytochrome P450 reductase/O2. Anaerobic heme-HO-1 complex with 1 eq produces an enzyme-bound intermediate identified spectroscopic methods α-meso-hydroxyheme. This first direct evidence for HO-1-catalyzed formation α-meso-Hydroxyheme exists mixture Fe(III) phenolate, keto anion, Fe(II) π neutral radical resonance structures....

Nitric oxide reductase (NOR) from Paracoccus denitrificans is a transmembrane heterodimer containing low-spin heme c, b, high-spin and non-heme iron. Protein sequence similarities between NOR the cytochrome oxidase superfamily suggest catalytic center of NO reduction to be dinuclear b/non-heme iron site two hemes facilitate electron transfer. The EPR-silent character ferric b believed due an antiferromagnetic coupling these metal centers via bridging ligand. Soret or red excitations on fully...

The H25C and H25Y mutants of human heme oxygenase-1 (hHO-1), in which the proximal iron ligand is replaced by a cysteine or tyrosine, have been expressed characterized. Resonance Raman studies indicate that ferric complexes these proteins, like complex H25A mutant but unlike wild type, are 5-coordinate high-spin. Labeling with 54Fe confirms protein thiolate. Resonance-enhanced tyrosinate modes resonance spectrum H25Y·heme provide direct evidence for ligation this protein. reduced to ferrous...

Flavodiiron proteins (FDPs) catalyze reductive scavenging of dioxygen and nitric oxide in air-sensitive microorganisms. FDPs contain a distinctive non-heme diiron/flavin mononucleotide (FMN) active site. Alternative mechanisms for the reductase (NOR) activity consisting either protonation diiron-bridging hyponitrite or "super-reduction" diferrous-dinitrosyl by proximal FMNH(2) rate-determining step have been proposed. To test these alternative mechanisms, we examined deflavinated FDP...

The extreme limitation of free iron has driven various pathogens to acquire from the host in form heme. Specifically, several Gram-negative secrete a heme binding protein known as HasA scavenge extracellular environment and transfer it receptor HasR for import into bacterial cell. Structures heme-bound apo-HasA homologues show that iron(III) ligands, His32 Tyr75, reside on loops extending core significant conformational change must occur at loop upon binding. Here, we investigate kinetics...

When challenged by low-iron conditions several Gram-negative pathogens secrete a hemophore (HasA) to scavenge hemin from its host and deliver it receptor (HasR) on their outer membrane for internalization. Here we report results studies aimed at probing the structural dynamic processes play in loading of apo-hemophore secreted P. aeruginosa (apo-HasAp) with hemin. The structure apo-HasAp shows large conformational change loop harboring axial ligand His32 relative holo-HasAp, whereas bearing...

Cellular dinitrosyl iron complexes (DNICs) have long been considered NO carriers. Although other physiological roles of DNICs postulated, their chemical functionality outside transfer has not demonstrated thus far. Here we report the unprecedented dioxygen reactivity a N-bound {Fe(NO)2}10 DNIC, [Fe(TMEDA)(NO)2] (1). In presence O2, 1 becomes nitrating agent that converts 2,4,-di-tert-butylphenol to 2,4-di-tert-butyl-6-nitrophenol via formation putative iron-peroxynitrite...

The activation of dioxygen by FeII(Me3TACN)(S2SiMe2) (1) is reported. Reaction 1 with O2 at −135 °C in 2-MeTHF generates a thiolate-ligated (peroxo)diiron complex FeIII2(O2)(Me3TACN)2(S2SiMe2)2 (2) that was characterized UV–vis (λmax = 300, 390, 530, 723 nm), Mössbauer (δ 0.53, |ΔEQ| 0.76 mm s–1), resonance Raman (RR) (ν(O–O) 849 cm–1), and X-ray absorption (XAS) spectroscopies. Complex 2 distinct from the outer-sphere oxidation product 1ox (UV–vis 435, 520, 600 0.45, 3.6 EPR (S 5/2, g...

Significance Nitric oxide reductases (NORs) catalyze the reduction of NO as part denitrification cycle, while structurally related heme-copper oxidases (HCOs) oxygen during respiration. Despite decades investigation into structure/function HCOs and NORs, factors governing their reaction specificity remain unknown. By tuning E°′ a biosynthetic model NOR in myoglobin using electrochemical, spectroscopic, computational methods to understand impact such tuning, this work reveals heme key...

The origin of the unusual regioselectivity heme oxygenation, i.e. oxidation to δ-biliverdin (70%) and β-biliverdin (30%), that is exhibited by oxygenase from Pseudomonas aeruginosa (pa-HO) has been studied 1H NMR, 13C resonance Raman spectroscopies. Whereas indicates heme−iron ligation in pa-HO homologous observed previously α-hydroxylating oxygenases, NMR spectroscopic studies suggest this enzyme seated a manner distinct for all other enzymes which structure known. In pa-HO, rotated...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTNitric Oxide Reductase from Paracoccus denitrificans Contains an Oxo-Bridged Heme/Non-Heme Diiron CenterPierre Moënne-Loccoz, Oliver-M. H. Richter, Hong-wei Huang, Ian M. Wasser, Reza A. Ghiladi, Kenneth D. Karlin, and Simon de VriesView Author Information Department of Biochemistry Molecular Biology Oregon Graduate Institute Science Technology Beaverton, 97006 Kluyver Laboratory for Biotechnology Delft University 2628 BC Delft, The...

CYP119 from <i>Sulfolobus solfataricu</i>s, the first thermophilic cytochrome P450, is stable at up to 85 °C. UV-visible and resonance Raman show enzyme in low spin state only modestly shifts high higher temperatures. Styrene causes a small shift, but T₁ NMR studies confirm that styrene bound active site. catalyzes H₂O₂-dependent epoxidation of styrene, <i>cis</i>-β-methylstyrene, and<i>cis</i>-stilbene with retention stereochemistry. This catalytic activity...