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 The mechanism of reaction of fully reduced membrane-bound cytochrome oxidase with oxygen at 176K

1978 ◽  
Vol 173 (3) ◽  
pp. 799-810 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Cytochrome Oxidase ◽  
Random Distribution ◽  
Linear Optimization ◽  
Valence States ◽  
Mechanism Of Reaction ◽  
Relative Absorption ◽  
Sequential Mechanism ◽  
Membrane Bound ◽  
Good Determination

1. The results of non-linear optimization studies on the mechanism of reaction of fully reduced cytochrome oxidase with O2 at 176K are presented. The analysis is carried out on data obtained by means of dual-wavelength multi-channel spectroscopy at three wavelength pairs (604-630, 608-630 and 830-940 nm) and at three O2 concentrations (60, 200 and 1180 micron). The only model that satisfies the triple requirement of a standard deviation within the standard error of the experimental data, good determination of the optimized parameters and a random distribution of residuals is a three-species 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 low-temperature trapping, e.p.r. and magnetic-susceptibility studies, the possible valence states of the metal centres in each of the intermediates are discussed.

scholarly journals The kinetics and thermodynamics of the reaction of solid-state fully reduced membrane-bound cytochrome oxidase with carbon monoxide as studied by dual-wavelength multichannel spectroscopy and flash photolysis

1978 ◽  
Vol 175 (2) ◽  
pp. 709-725 ◽  
Author(s):  
G M Clore ◽  
E M Chance
Keyword(s):  
Solid State ◽  
Cytochrome Oxidase ◽  
Flash Photolysis ◽  
Linear Optimization ◽  
Dual Wavelength ◽  
Mechanism Of Reaction ◽  
Sequential Mechanism ◽  
Membrane Bound ◽  
Good Determination

1. The results of non-linear optimization studies on the mechanism of reaction of solid-state fully reduced membrane-bound cytochrome oxidase with CO over the 178–203 K range are presented. The analysis is carried out on data obtained by dual-wavelength multichannel spectroscopy at three wavelength pairs (444–463 nm, 590–630 nm and 608–630 nm), which yield three distinct progress curves. The only model that satisfies the triple requirement of a standard deviation within the standard error of the data, a random distribution of residuals and good determination of the optimized parameters is a two-species sequential mechanism: flash photolysis yields unliganded cytochrome oxidase and free CO, which then recombine to form species Ic; Ic is then converted into species IIc, which is identical with the cytochrome oxidase-CO complex existing before flash photolysis. All the thermodynamic parameters describing this model are calculated. 2. On the basis of the data obtained from this paper, together with data from potentiometric studies, magnetic susceptibility measurements and i.r. spectroscopy, the chemical identity of the species is suggested.

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 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.

Tunable emission color and mixed valence state via the modified activator site in the AlN-doped Sr3SiO5:Eu phosphor

RSC Advances ◽  
2016 ◽  
Vol 6 (39) ◽  
pp. 33076-33082 ◽  
Author(s):  
Wei Li ◽  
Jin Wang ◽  
Haoran Zhang ◽  
Yingliang Liu ◽  
Bingfu Lei ◽  
...  
Keyword(s):  
Valence State ◽  
Mixed Valence ◽  
Mixed Valence State ◽  
Valence States ◽  
Emission Color ◽  
Co Doped ◽  
Tunable Emission

Mixed valence states of Eu2+/Eu3+ and tunable emission colors were obtained based on the activator-site modification in the AlN co-doped Sr3SiO5:Eu phosphor.

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