Abstract Respiratory complex I converts the free energy of ubiquinone reduction by NADH into a proton motive force, redox reaction catalyzed flavin mononucleotide(FMN) and chain seven iron–sulfur centers. Electron transfer rates between centers were determined ultrafast freeze‐quenching analysis EPR UV/Vis spectroscopy. The rapidly oxidizes three molecules. electron‐tunneling rate most distant in middle depends on state center N2 at end chain, is sixfold slower when reduced. conformational...

Abstract The amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins bioactive peptides exhibits high affinity towards Cu II ions have been implicated human physiology. Little is known, however, about the rate exact mechanism of formation such complexes. We used stopped‐flow microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic electrochemical data to demonstrate partially coordinated intermediate complexes formed...

The molecular biology and biochemistry of denitrification in gram-negative bacteria has been studied extensively. However, little is known about this process gram-positive bacteria. We have purified the NO reductase from cytoplasmic membrane bacterium Bacillus azotoformans. enzyme consists two subunits with apparent masses 16 40 kDa based on SDS−PAGE. Analytical spectroscopic determinations revealed presence one non-heme iron, copper atoms b-type hemes per complex. Heme c was absent. Using...

The membrane-bound NO reductase from the hyperthermophilic denitrifying archaeon Pyrobaculum aerophilum was purified to homogeneity. enzyme displays MQH2:NO oxidoreductase (qNOR) activity, consists of a single subunit, and contains heme nonheme iron in 2:1 ratio. combined results EPR, resonance Raman, UV-visible spectroscopy show that one hemes is bis-His-coordinated low spin (gz = 3.015; gy 2.226; gx 1.45), whereas other adopts high configuration. also center, which oxidized...

Nitrate reductases (Nars) belong to the DMSO reductase family of molybdoenzymes. The hyperthermophilic denitrifying archaeon Pyrobaculum aerophilum exhibits nitrate (Nar) activity even at WO(4)(2-) concentrations that are inhibitory bacterial Nars. In this report, we establish enzyme purified from cells grown with 4.5 μM contains W as metal cofactor but is otherwise identical Mo-Nar previously P. low concentrations. coordinated by a bis-molybdopterin guanine dinucleotide cofactor. W-Nar has...

The heme enzyme chlorite dismutase (Cld) catalyzes O-O bond formation as part of the conversion toxic (ClO2 -) to chloride (Cl-) and molecular oxygen (O2). Enzymatic is rare in nature, therefore, reaction mechanism Cld great interest. Microsecond timescale pre-steady-state kinetic experiments employing from Azospira oryzae (AoCld), natural substrate chlorite, model peracetic acid (PAA) reveal distinct intermediates. AoCld forms a complex with PAA rapidly, which cleaved heterolytically yield...

To afford mechanistic studies in enzyme kinetics and protein folding the microsecond time domain we have developed a continuous-flow time-scale mixing instrument with an unprecedented dead-time of 3.8 ± 0.3 μs. The employs micro-mixer 2.7 μs integrated 30 mm long flow-cell 109 μm optical path length constructed from two parallel sheets silver foil; it produces ultraviolet-visible spectra that are linear absorbance up to 3.5 spectral resolution 0.4 nm. Each spectrum corresponds different...

We used a series of modified/substituted GGH analogues to investigate the kinetics Cu(II) binding ACTUN peptides. Rules for rate modulation by 1st and 2nd sphere interactions were established, providing crucial insight into elucidation reaction mechanism its contribution biological copper transport.

Paracoccus pantotrophus cytochrome cd1 is a nitrite reductase found in the periplasm of many denitrifying bacteria. It catalyzes reduction to nitric oxide during denitrification part biological nitrogen cycle. Previous studies early millisecond intermediates reaction have shown, by comparison with pH 7.0, that at optimum pH, approximately 6, earliest were lost dead time instrument. Access points (∼100 μs) through use an ultra-rapid mixing device has identified spectroscopically novel...

Chlorite dismutase is a heme enzyme that catalyzes the conversion of toxic compound ClO2- (chlorite) to innocuous Cl- and O2. The reaction very rare case enzymatic O-O bond formation, which has sparked interest elucidate mechanism using pre-steady-state kinetics. During stopped-flow experiments, spectroscopic structural changes were observed in absence substrate time range from milliseconds minutes. These effects are consequence illumination with UV-visible light during experiment. spectrum...

Abstract Der Atmungskettenkomplex I wandelt die freie Energie, bei der Reduktion von Ubichinon durch NADH frei wird, in einen Protonengradienten über Membran um. Die biologische Redoxreaktion wird einem Flavinmononukleotid und einer Kette sieben Eisen‐Schwefel‐Zentren katalysiert. Elektronentransfergeschwindigkeiten zwischen den Zentren wurden eine schnelle “Freeze‐Quench”‐Methode Analyse Proben mittels EPR‐ UV/Vis‐Spektroskopie bestimmt. Komplex oxidiert sehr schnell drei Moleküle NADH;...

Soluble quinoprotein (PQQ-containing) glucose dehydrogenase (sGDH, EC 1.1.99.35) catalyzes the oxidation of β-d-glucose to d-glucono-δ-lactone. Although sGDH has many analytical applications, relationship between activity and substrate concentration is not well established. Previous steady-state kinetic studies revealed a negative cooperativity effect which recently been ascribed subunit interaction. To investigate this conclusion, stopped-flow experiments were carried out on reaction in...

The Birch reduction is a widely used synthetic tool to reduce arenes 1,4-cyclohexadienes. Its harsh cryogenic reaction conditions and the dependence on alkali metals have motivated researchers explore alternative approaches. In anaerobic aromatic compound degrading microbes, class II benzoyl-coenzyme A (CoA) reductases (BCRs) benzoyl-CoA conjugated cyclohexa-1,5-diene-1-carboxyl-CoA (1,5-dienoyl-CoA) at tungsten-bis-metallopterin (MPT) cofactor. Though previous structure-based computational...

Abstract Chlorite dismutase is a unique heme enzyme that catalyzes the conversion of chlorite to chloride and molecular oxygen. The highly specific for but has been known bind several anionic neutral ligands iron. In pH study, changed color from red green in acetate buffer 5.0. cause this change was uncovered using UV–visible EPR spectroscopy. presence showed spectrum: redshift hyperchromicity Soret band 391 404 nm blueshift charge transfer CT1 647 626 nm. Equilibrium binding titrations with...

Abstract The amino‐terminal copper and nickel/N‐terminal site (ATCUN/NTS) present in proteins bioactive peptides exhibits high affinity towards Cu II ions have been implicated human physiology. Little is known, however, about the rate exact mechanism of formation such complexes. We used stopped‐flow microsecond freeze‐hyperquenching (MHQ) techniques supported by steady‐state spectroscopic electrochemical data to demonstrate partially coordinated intermediate complexes formed...

Bioanorganische Chemie W. Bal et al. demonstrieren auf S. 11330, dass die Bindung von CuII an GGH-Peptid, ein prototypischesATCUN/NTS-Motiv, über partiell koordinierte Spezies verläuft. Eine 2N-koordinierte mit CuII/CuI-Redoxaktivität ist lange gesuchte reaktive Zwischenstufe beim extrazellulären Kupfertransport.