scholarly journals Characterization of the intermediates in the reaction of mixed-valence state soluble cytochrome oxidase with oxygen at low temperatures by optical and electron-paramagnetic-resonance spectroscopy

1980 ◽  
Vol 185 (1) ◽  
pp. 155-167 ◽  
Author(s):  
G M Clore ◽  
L E Andréasson ◽  
B Karlsson ◽  
R Aasa ◽  
B G Malmström
Keyword(s):  
Cytochrome Oxidase ◽  
Valence State ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Mixed Valence ◽  
Spectroscopic Properties ◽  
Resonance Spectroscopy ◽  
Difference Spectra ◽  
Paramagnetic Resonance ◽  
Mixed Valence State ◽  
The Difference

The reaction of soluble mixed-valence-state (a3+CuA2+.CuB+A32+) cytochrome oxidase with O2 at low temperature was studied by optical and e.p.r. spectroscopy. The existence of three intermediates [Clore & Chance (1978) Biochem. J. 173, 799-8101] was confirmed. From the e.p.r data it is clear that cytochrome a and CuA remain in the low-spin ferric and cupric states respectively throughout the reaction. No e.p.r. signals attributable to cytochrome a3 or CuB were seen in the intermediates. The difference spectra (intermediates minus unliganded mixed-valence-state cytochrome oxidase) and absolute spectra of the three intermediates were obtained. The chemcal nature of the three intermediates is discussed in terms of their spectroscopic properties. A catalytic cycle for cytochrome oxidase is proposed.

scholarly journals Characterization of the intermediates in the reaction of membrane-bound mixed-valence-state cytochrome oxidase with oxygen at low temperatures by optical spectroscopy in the visible region

1980 ◽  
Vol 187 (3) ◽  
pp. 617-622 ◽  
Author(s):  
G M Clore
Keyword(s):  
Cytochrome Oxidase ◽  
Optical Spectroscopy ◽  
Valence State ◽  
Mixed Valence ◽  
Visible Region ◽  
Difference Spectrum ◽  
Difference Spectra ◽  
Mixed Valence State ◽  
Membrane Bound ◽  
The Difference

The ‘pure’ difference spectra of the three species, IM, IIM and IIIM, formed in the low-temperature reaction of membrane-bound mixed-valence-state cytochrome oxidase with O2 relative to unliganded membrane-bound mixed-valence-state cytochrome oxidase were characterized by optical spectroscopy in the visible region. The difference spectrum of species IM was characterized by a peak at 590 nm and a trough at 608 nm, that of species IIM by a peak at 606 nm, and that of species IIIM by a peak at 610 nm. A comparison with the difference spectra of species IIM and IIIM obtained with soluble cytochrome oxidase [Clore, Andréasson, Karlsson, Aasa & Malmström (1980) Biochem. J. 185, 155-167] revealed small but significant differences in the peak positions and bandwidths of the 605-610 nm absorption band.

scholarly journals The Structures, Spectroscopic Properties, and Photodynamic Reactions of Three [RuCl(QN)NO]−Complexes (HQN = 8-Hydroxyquinoline and Its Derivatives) as Potential NO-Donating Drugs

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Leilei Xie ◽  
Lifang Liu ◽  
Wenming Wang ◽  
Zhiou Ma ◽  
Liqun Xu ◽  
...  
Keyword(s):  
Density Functional ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Energy Levels ◽  
Spectroscopic Properties ◽  
Resonance Spectroscopy ◽  
Electronic Effects ◽  
Paramagnetic Resonance ◽  
Time Resolved ◽  
Potential Applications ◽  
Electron Paramagnetic

The structures and spectral properties of three ruthenium complexes with 8-hydroxyquinoline (Hhqn) and their derivatives 2-methyl-8-quinolinoline (H2mqn) and 2-chloro-8-quiolinoline (H2cqn) as ligands (QN = hqn, 2mqn, or 2cqn) were calculated with density functional theory (DFT) at the B3LYP level. The UV-Vis and IR spectra of the three [RuCl(QN)NO]−complexes were theoretically assigned via DFT calculations. The calculated spectra reasonably correspond to the experimentally measured spectra. Photoinduced NO release was confirmed through spin trapping of the electron paramagnetic resonance spectroscopy (EPR), and the dynamic process of the NO dissociation upon photoirradiation was monitored using time-resolved infrared (IR) spectroscopy. Moreover, the energy levels and related components of frontier orbitals were further analyzed to understand the electronic effects of the substituent groups at the 2nd position of the ligands on their photochemical reactivity. This study provides the basis for the design of NO donors with potential applications in photodynamic therapy.

scholarly journals Compound C2, a product of the reaction of oxygen and the mixed-valence state of cytochrome oxidase. Optical evidence for a type-I copper

1979 ◽  
Vol 177 (3) ◽  
pp. 931-941 ◽  
Author(s):  
B Chance ◽  
C Saronio ◽  
J S Leigh
Keyword(s):  
Charge Transfer ◽  
Cytochrome Oxidase ◽  
Valence State ◽  
Mixed Valence ◽  
Type I ◽  
Blue Copper ◽  
Mixed Valence State ◽  
Charge Transfer Interaction ◽  
A Charge ◽  
Reduced State

Compound C2 is a product of the reaction of O2 and the mixed-valence state of cytochrome oxidase. The mixed-valence state of membrane-bound cytochrome oxidase is obtained at -24 degrees C, by using either ferricyanide or yeast peroxidase complex ES as oxidants, and the configurations of oxidized haem a and its associated copper (a3+Cua2+) and of reduced haem a3 and its associated copper (ac3+.CO.Cua3+) are obtained. The mixed-valence-state cytochrome oxidase mixed with O2 at -24 degrees C and flash-photolysed at -60 to -100 degrees C reacts with O2 and initially forms an oxy compound (A2) similar to that formed from the fully reduced state (A1). Thereafter the course of the reaction differs from that obtained in the fully reduced state, and absorbance increases are observed at 740–750 nm and 609 nm and a decrease at 444 nm, with no increase in absorbance at 655 nm. One possible attribution of the absorbance increases is to charge-transfer interaction between the iron of haem a3 and the copper associated with haem a3, Cua3(2+), having properties of a type-I ‘blue’ copper. A possible attribution of the decrease in absorbance at 444 nm is to liganding of a3(2+). A related explanation is that the 609 nm absorbance involves a charge-transfer interaction of both iron and copper as a mixed-valence binuclear complex, Cua3, having properties of a non-blue copper. Intermediates in addition to Compound C2 are not yet identifiable by chemical or spectroscopic tests. The kinetic and equilibrium properties of Compound C2 are described.

scholarly journals The mechanism of reaction of ferricyanide-pretreated mixed-valence-state membrane-bound cytochrome oxidase with oxygen at 173 K

1978 ◽  
Vol 173 (3) ◽  
pp. 811-820 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Cytochrome Oxidase ◽  
Valence State ◽  
Linear Optimization ◽  
Mixed Valence ◽  
Mixed Valence State ◽  
Optical Wavelength ◽  
Valence States ◽  
Mechanism Of Reaction ◽  
Sequential Mechanism ◽  
Good Determination

1. The results of non-linear optimization studies on the mechanism of reaction of ferricyanide-pretreated mixed-valence-state cytochrome oxidase with O2 at 173 K are presented. The analysis is carried out on data obtained by means of dual-wavelength multi-channel spectroscopy at four wavelength pairs (444-463 nm, 604-630 nm, 608-630 nm and 830-940 nm) and at two O2 concentrations (360 micron and 520 micron). The only model that satisfies the triple requirement of a standard deviation within the standard error of the experimental data, a random distribution of residuals and good determination of the optimized parameters, is a three-intermediate sequential mechanism. 2. On the basis of the optimized values of the relative absorption coefficients of the intermediates at each wavelength obtained from the present paper together with data from optical wavelength scanning and e.p.r. spectroscopy obtained by low-temperature trapping studies, the possible valence states of the metal centres in each of the intermediates are discussed.

scholarly journals An antimycin A- and cyanide-resistant variant of Candida utilis arising during copper-limited growth

1973 ◽  
Vol 134 (4) ◽  
pp. 1051-1061 ◽  
Author(s):  
J. A. Downie ◽  
P. B. Garland
Keyword(s):  
Cytochrome Oxidase ◽  
Candida Utilis ◽  
Alternative Oxidase ◽  
Growth Parameters ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Limited Growth ◽  
Paramagnetic Resonance ◽  
Resistant Variant ◽  
Electron Paramagnetic

1. During copper-limited growth of Candida utilis in continuous culture on a non-fermentable carbon and energy source there is a selective pressure favouring the emergence of variants that are less dependent on copper. 2. We describe the properties of such a variant that by-passes cytochrome oxidase (EC 1.9.3.1) by utilizing an alternative oxidase communicating with the respiratory chain at about the level of cytochrome b. 3. Both direct studies of isolated mitochondria and calculations based on growth parameters showed that only one of the normal three phosphorylation sites was active. This site was localized between NADH and the cytochromes. 4. Growth of the variant with copper-supplemented media resulted in the return of cytochrome oxidase but not the loss of the alternative oxidase. 5. The alternative oxidase is inhibited by substituted benzhydroxamic acids. 6. Submitochondrial particles from the variant did not exhibit any novel electron-paramagnetic-resonance-spectroscopy features at about g=2.0 either at 80°K or 12°K.

scholarly journals Some magnetic properties of Pseudomonas cytochrome oxidase

1979 ◽  
Vol 177 (1) ◽  
pp. 29-39 ◽  
Author(s):  
T A Walsh ◽  
M K Johnson ◽  
C Greenwood ◽  
D Barber ◽  
J P Springall ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Magnetic Circular Dichroism ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Parallel Study ◽  
Paramagnetic Resonance ◽  
Redox States ◽  
Electron Paramagnetic

The magnetic properties of the haem groups of Pseudomonas cytochrome oxidase and its cyanide-bound derivatives were studied in both the oxidized and reduced states by means of m.c.d. (magnetic circular dichroism) at low temperatures. In addition, the oxidized forms of the enzyme were also investigated by e.p.r. (electron-paramagnetic-resonance) spectroscopy, and a parallel study, using both e.p.r. and m.c.d., was made on Pseudomonas cytochrome c-551 to aid spectral assignments. For ascorbate-reduced Pseudomonas cytochrome oxidase, the temperature-independence of those features in the m.c.d. spectrum corresponding to the haem c, and the temperature-dependence of those signals corresponding to the haem d1, showed the former to be low-spin and the latter to be high-spin (s = 2). However, addition of cyanide to the reduced enzyme gave a form of the protein that was completely low-spin. The e.p.r. and m.c.d. sectra of oxidized Pseudomonas cytochrome oxidase and its cyanide derivative were consistent with the haem c and d1 components being low-spin in both cases. Pseudomonas cytochrome c-551 was found to be low-spin in both its oxidized and reduced redox states.

Electron paramagnetic resonance study of radicals derived from 2- and 3-fluoropropene

1993 ◽  
Vol 71 (6) ◽  
pp. 809-813 ◽  
Author(s):  
Peter Smith ◽  
Cynthia Ann Hougum ◽  
Art Aresh Hosseinian
Keyword(s):  
Electron Paramagnetic Resonance ◽  
General Formula ◽  
Continuous Flow ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Electron Paramagnetic Resonance Study ◽  
Reaction System ◽  
Spectroscopic Properties ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Using the TiCl3–H2O2, –NH2OH, −Na2S2O8, and −H2O2/Na2SO3, continuous-flow, radical-generating methods at 25 °C, we have successfully characterized by electron paramagnetic resonance spectroscopy radicals formed by the reaction of each of the substrates 2- and 3-fluoropropene with the radicals •OH, •NH3+, •OSO3−, and •SO3−, respectively. With 2-and 3-fluoropropene, respectively, the radicals identified were of general formula CH2(X)ĊFCH3 and CH2(X)ĊHCH2F where -X is the added group, except that treatment of 3-fluoropropene with the TiCl3–H2O2 reaction system also yielded •CH2CH(X)CH2F. The results obtained are discussed in terms of the effect of the presence of the fluorine substituent on both the apparent reactivity of the substrate molecules towards the radical-generating systems and the spectroscopic properties of the radicals observed.

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