Spectroscopic evidehce for an oxygen bridge between the iron atom of cytochrome a3 and CuB in the class C group of compounds formed in the reaction of mixed valence state cytochrome oxidase with oxygen

1981 ◽  
Vol 55 ◽  
pp. L47-L49
Author(s):  
G.Marius Clore ◽  
Michel Denis
Keyword(s):  
Cytochrome Oxidase ◽  
Iron Atom ◽  
Valence State ◽  
Mixed Valence ◽  
Mixed Valence State ◽  
Oxygen Bridge ◽  
Class C

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 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.

Theory for the mixed-valence state

1979 ◽  
Vol 40 (C5) ◽  
pp. C5-374-C5-374 ◽  
Author(s):  
C. M. Varma
Keyword(s):  
Valence State ◽  
Mixed Valence ◽  
Mixed Valence State

MIXED VALENCE STATE OF Sm ON THE SURFACE OF AMORPHOUS La80-xSmxAu20 ALLOYS

1980 ◽  
Vol 41 (C8) ◽  
pp. C8-799-C8-802 ◽  
Author(s):  
G. Krill ◽  
A. Amamou ◽  
A. Berrada ◽  
J. Durand ◽  
N. Hassanain
Keyword(s):  
Valence State ◽  
Mixed Valence ◽  
Mixed Valence State

scholarly journals Mixed-Valence State of Europium in the Misfit Layer Compound (EuS)1.173NbS2.

ChemInform ◽  
2003 ◽  
Vol 34 (20) ◽  
Author(s):  
Laurent Cario ◽  
Pierre Palvadeau ◽  
Alain Lafond ◽  
Catherine Deudon ◽  
Yves Moelo ◽  
...  
Keyword(s):  
Valence State ◽  
Mixed Valence ◽  
Layer Compound ◽  
Mixed Valence State
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