Nature of the Coupling between the High-Spin Fe(III) Heme and CuB(II) in the Active Site of Terminal Oxidases:  Dual-Mode EPR Spectra of Fluoride Cytochromebo3

1998 ◽  
Vol 120 (17) ◽  
pp. 4232-4233 ◽  
Author(s):  
Vasily S. Oganesyan ◽  
Clive S. Butler ◽  
Nicholas J. Watmough ◽  
Colin Greenwood ◽  
Andrew J. Thomson ◽  
...  
Keyword(s):  
High Spin ◽  
Active Site ◽  
Epr Spectra ◽  
Dual Mode ◽  
Terminal Oxidases

Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles

1980 ◽  
Vol 45 (6) ◽  
pp. 1669-1676 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Oxidation ◽  
Spin Polarization ◽  
High Spin ◽  
Epr Spectroscopy ◽  
Half Life ◽  
Electrochemical Behaviour ◽  
Epr Spectra ◽  
Electrochemical Generation ◽  
Splitting Constant ◽  
Reduced Temperature

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.

scholarly journals Nitric Oxide Does Not Inhibit but Is Metabolized by the Cytochrome bcc-aa3 Supercomplex

2020 ◽  
Vol 21 (22) ◽  
pp. 8521 ◽  
Author(s):  
Elena Forte ◽  
Alessandro Giuffrè ◽  
Li-shar Huang ◽  
Edward A. Berry ◽  
Vitaliy B. Borisov
Keyword(s):  
Nitric Oxide ◽  
Active Site ◽  
Protective Role ◽  
Terminal Oxidase ◽  
O2 Consumption ◽  
Turnover Number ◽  
Terminal Oxidases ◽  
Reducing Conditions ◽  
No Consumption

Nitric oxide (NO) is a well-known active site ligand and inhibitor of respiratory terminal oxidases. Here, we investigated the interaction of NO with a purified chimeric bcc-aa3 supercomplex composed of Mycobacterium tuberculosis cytochrome bcc and Mycobacterium smegmatisaa3-type terminal oxidase. Strikingly, we found that the enzyme in turnover with O2 and reductants is resistant to inhibition by the ligand, being able to metabolize NO at 25 °C with an apparent turnover number as high as ≈303 mol NO (mol enzyme)−1 min−1 at 30 µM NO. The rate of NO consumption proved to be proportional to that of O2 consumption, with 2.65 ± 0.19 molecules of NO being consumed per O2 molecule by the mycobacterial bcc-aa3. The enzyme was found to metabolize the ligand even under anaerobic reducing conditions with a turnover number of 2.8 ± 0.5 mol NO (mol enzyme)−1 min−1 at 25 °C and 8.4 µM NO. These results suggest a protective role of mycobacterial bcc-aa3 supercomplexes against NO stress.

EPR spectra of low-symmetry tetrahedral high-spin cobalt(II) in a cinchoninium tetrachlorocobaltate(II) dihydrate single crystal

1985 ◽  
Vol 24 (24) ◽  
pp. 4009-4012 ◽  
Author(s):  
H. Drulis ◽  
K. Dyrek ◽  
K. P. Hoffmann ◽  
Stanislaw K. Hoffmann ◽  
A. Weselucha-Birczynska
Keyword(s):  
Single Crystal ◽  
High Spin ◽  
Epr Spectra ◽  
Low Symmetry

Spectroscopic studies on two-iron ferredoxins

1974 ◽  
Vol 7 (4) ◽  
pp. 443-504 ◽  
Author(s):  
R. H. Sands ◽  
W. R. Dunham
Keyword(s):  
High Spin ◽  
Active Site ◽  
Active Sites ◽  
Spectroscopic Studies ◽  
Transport Proteins ◽  
Distorted Tetrahedron ◽  
X Ray ◽  
Iron Proteins ◽  
Electron Transport Proteins ◽  
Reduced State

The application of magnetic resonance techniques to biological systems has permitted a detailed study of the nature of the active sites of many proteins that had not been possible previously. Among these is the whole class of iron—sulphur proteins which have been implicated as electron transport proteins in a variety of fundamental processes: photosynthesis, hydroxylation and nitrogen fixation to name but a few.The single-iron proteins in this class, the rubredoxins, have been studied extensively by chemical, spectroscopic and X-ray crystallographic techniques (Lovenberg, 1973), and the active site is composed of a single iron atom bound in a distorted tetrahedron of cysteine sulphur ligands. The iron is high-spin ferric in the oxidized state and high-spin ferrous in the reduced state. This structure is shown in Fig. I (α).

ChemInform Abstract: EPR Spectra of Low-Symmetry Tetrahedral High-Spin Cobalt(II) in a Cinchoninium Tetrachlorocobaltate(II) Dihydrate Single Crystal.

1986 ◽  
Vol 17 (11) ◽  
Author(s):  
H. DRULIS ◽  
K. DYREK ◽  
K. P. HOFFMANN ◽  
S. K. HOFFMANN ◽  
A. WESELUCHA-BIRCZYNSKA
Keyword(s):  
Single Crystal ◽  
High Spin ◽  
Epr Spectra ◽  
Low Symmetry
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