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

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.

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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

Biochemical Journal ◽

10.1042/bj1750709 ◽

1978 ◽

Vol 175 (2) ◽

pp. 709-725 ◽

Cited By ~ 11

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.

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

Biochemical Journal ◽

10.1042/bj1730811 ◽

1978 ◽

Vol 173 (3) ◽

pp. 811-820 ◽

Cited By ~ 13

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.

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Low-temperature kinetics of the reaction of oxygen and solubilized cytochrome oxidase

Biochemical Journal ◽

10.1042/bj1710787 ◽

1978 ◽

Vol 171 (3) ◽

pp. 787-798 ◽

Cited By ~ 26

Author(s):

B Chance ◽

C Saronio ◽

J S Leigh ◽

W J Ingledew ◽

T E King

Keyword(s):

Cytochrome Oxidase ◽

Mixed Valence ◽

Similar Species ◽

Absorption Bands ◽

Compound C ◽

Valence States ◽

Membrane Bound ◽

Peroxy Compounds ◽

Band Characteristic ◽

Kinetics Of

The reaction of solubilized cytochrome oxidase in the fully reduced state with O2 at low temperatures reveals components with characteristics similar to those observed with the membrane-bound oxidase, namely compounds A and B, which are proposed to be ‘oxy’ and ‘peroxy’ compounds respectively. Similar species are identified in both solubilized and membrane-bound oxidases; the reaction velocity constant for the reation with O2 and the dissociation constant are decreased 2-3-fold in the solubilied preparation as compared with the membrane-bound species, owing to decreased reactivity towards O2 in the former. The oxidase prepared in the mixed-valence state shows the distinctive absorption band characteristic of compound C, identified in the membrane-bound oxidase. The assignment of the alpha, beta, gamma and near-i.r. absorption bands to possible valence states of these compounds is made.

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Characterization of the low-temperature intermediates of the reaction of fully reduced soluble cytochrome oxidase with oxygen by electron-paramagnetic-resonance and optical spectroscopy

Biochemical Journal ◽

10.1042/bj1850139 ◽

1980 ◽

Vol 185 (1) ◽

pp. 139-154 ◽

Cited By ~ 86

Author(s):

G M Clore ◽

L E Andréasson ◽

B Karlsson ◽

R Aasa ◽

B G Malmström

Keyword(s):

Low Temperature ◽

Cytochrome Oxidase ◽

Linear Optimization ◽

Stable State ◽

Reaction Scheme ◽

Optimization Techniques ◽

Optical Data ◽

Paramagnetic Resonance ◽

Valence States

The reaction of fully reduced soluble bovine heart cytochrome oxidase with O2 at 173K was investigated by low-temperature optical and e.p.r. spectroscopy, and the kinetics of the reaction were analysed by non-linear optimization techniques. The only e.p.r. signals seen during the course of the reaction are those attributable to low-spin cytochrome a3+ and CuA2+. Quantitative analysis of e.p.r. signals shows that, at the end point of the reaction at 173K, nearly 100% of CuA is in the cupric state but only about 40% of cytochrome a is in the ferric low-spin state. The optical spectra recorded at this stage of the reaction show incomplete oxidation of haem and the absence of a 655 nm absorption band. The only reaction scheme that accounts for both the e.p.r. and optical data is a four-intermediate mechanism involving a branching pathway. The reaction is initiated when fully reduced cytochrome oxidase reacts with O2 to form intermediate I. This is then converted into either intermediate IIA or intermediate IIB. Of these, intermediate IIB is a stable end product at 173 K, but intermediate IIA is converted into intermediate III, which is the stable state at 173 K in this branch of the mechanism. The kinetic analysis of the e.p.r. data allows the unambiguous assignments of the valence states of cytochrome a and CuA in the intermediates. Intermediate I contains cytochrome a2+ and CuA+, intermediate IIA contains low-spin cytochroma a3+ and CuA+, intermediate IIB contains cytochrome a2+ and CuA2+, and intermediate III contains low-spin cytochrome a3+ and CuA2+. The electronic state of the O2-binding CuBa3 couple during the reoxidation of cytochrome oxidase is discussed in terms of an integrated structure containing CuB, cytochrome a3 and O2.

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

Biochemical Journal ◽

10.1042/bj1750353a ◽

1978 ◽

Vol 175 (2) ◽

pp. 353.b1-353.b1

Keyword(s):

Cytochrome Oxidase ◽

Mechanism Of Reaction ◽

Membrane Bound

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The active site of membrane-bound meizothrombin. A fluorescence determination of its distance from the phospholipid surface and its conformational sensitivity to calcium and factor Va.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)39312-3 ◽

1990 ◽

Vol 265 (11) ◽

pp. 6210-6218

Author(s):

S A Armstrong ◽

E J Husten ◽

C T Esmon ◽

A E Johnson

Keyword(s):

Active Site ◽

Factor Va ◽

Fluorescence Determination ◽

Membrane Bound

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Determination of Valence States of Neptunium Ions in Solution by Controlled Potential Coulometry

Analytical Chemistry ◽

10.1021/ac60157a043 ◽

1960 ◽

Vol 32 (1) ◽

pp. 134-135 ◽

Cited By ~ 15

Author(s):

R. W. Stromatt

Keyword(s):

Valence States ◽

Controlled Potential ◽

Controlled Potential Coulometry

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Functional intermediates in the reaction of membrane-bound cytochrome oxidase with oxygen.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)40634-0 ◽

1975 ◽

Vol 250 (24) ◽

pp. 9226-9237 ◽

Cited By ~ 9

Author(s):

B Chance ◽

C Saronio ◽

JS Leigh

Keyword(s):

Cytochrome Oxidase ◽

Membrane Bound

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The Valance Determination of Cerium Ions in α-SiAlON by Electron Energy Loss Spectroscopy Analysis

Microscopy and Microanalysis ◽

10.1017/s1431927608089265 ◽

2008 ◽

Vol 14 (S3) ◽

pp. 19-22 ◽

Cited By ~ 3

Author(s):

H. Yurdakul ◽

S. Turan

Keyword(s):

Rare Earth ◽

Ionic Radius ◽

High Hardness ◽

Engineering Properties ◽

Secondary Phases ◽

Sintering Additive ◽

Valence States ◽

Domain Boundaries ◽

Spark Plasma

SiAlON ceramics have found applications in many different areas due to their excellent engineering properties such as high hardness, fracture toughness, good thermal shock and oxidation resistance. SiAlON exist mainly in two different polymorphs: a (MxSi12-(m+n)Al(m+n)OnN16-n; M: metal and rare earth cations, x≈0,35 and n≤1,35) and β (β-Si6-zAlzOzN8-z; 0≤z≤4). In general, stable alpha and beta phases separately as well as in combination of α and β are obtained by incorporation of metal and rare earth cations as sintering additives. The metal cations such as Li, Mg, Ca, Y, and most lanthanide cations with the exception of La, Ce, Pr and Eu are able to stabilise α-SiAlON structure. Ekstrom et al. 1991 found that cerium can not occupy interstitial sites in α-SiAlON structure due to the fact that ionic radius of Ce3+ (0.103 nm) is too large, whereas ionic radius of Ce4+ (0.080 nm) is too small to stabilise α-SiAlON structure. After this work, several studies carried out to incorporate cerium cations into α-SiAlON structure. It was shown that cerium cation alone can be incorporated into α-SiAlON if the samples are either fast cooled after sintering, or when the samples are spark plasma sintered. On the other hand, cerium can also be incorporated into the α-SiAlON structure when it is used as a sintering additive together with a smaller α-SiAlON stabiliser cation such as Yb or Ca. Similar results were observed in other multi-cation doped SiAlONS that non α-SiAlON stabiliser cations like Sr2+ (0.112 nm) and La3+ (0.106 nm) are able to stabilise α-SiAlON when used together with α-SiAlON stabiliser cations such as Ca or Yb. Although it was shown that cerium existed in mixed valance state at domain boundaries in Ce-doped and spark plasma sintered α-SiAlON, there is no work on the valance determination of cerium in sintered α-SiAlON which has no domain boundaries. Therefore, in this study; it was aimed to incorporate cerium into α-SiAlON structure by combining with Yb3+ and the determination of possible cerium valence states (Ce3+/Ce4+) in both α-SiAlON grains and secondary phases.

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