Determination of the heme spin states in cytochrome <i>c</i> oxidase using magnetic circular dichroism

Thomson, Andrew J.; Brittain, Thomas; Greenwood, C. T.; Springall, J.

doi:10.1016/0014-5793(76)80877-0

Cited by 32 publications

(26 citation statements)

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“…However, just as one of the unpaired electrons on high-spin haem a33+ is spin-coupled with the unpaired electron on CUB2+ resulting in the formation of an anti-ferromagnetically spin-coupled haemcopper dimer that is not visible by e.p.r. (Palmer et al, 1976;Thomson et al, 1976Thomson et al, , 1977Falk et al, 1977), it seems likely that one of the unpaired electrons on high-spin haem a33+ could also undergo spin-couplingwith the unpaired electronO2-resulting in the formation of an exchange-coupled complex of even spin (S = 2 or 3), which would be difficult or impossible to observe by e.p.r. (b) The intense absorption band at 606-609nm associated with intermediate IlIM (Chance et al, 1975b,c;Chance & Leigh, 1977;Denis & Chance, 1977 (d) The 655nm band, which, on the basis of e.p.r.…”

Section: Resultsmentioning

confidence: 99%

“…The other copper atom, termed CUB, is undetectable by e.p.r. (Aasa et al, 1976) and anti-ferromagnetically coupled to high-spin haem a33+ when in the cupric state (Palmer et al, 1976;Thomson et al, 1976Thomson et al, , 1977Falk et al, 1977). [The notation used to designate the two copper atoms is that of Clore & Chance (1978) and Palmer et al (1976), and will be used throughout the present paper.…”

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confidence: 99%

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

Clore¹,

Chance²

1978

Biochemical Journal

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1. The results of non-linear optimization studies on the mechanism of reaction of ferricyanide-pretreated mixed-valence-state cytochrome oxidase with 02 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, 604-630nm, 608-630nm and 830-940nm) and at two 02 concentrations (360,uM and 520AM). 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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Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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

Clore¹,

Chance²

1978

Biochemical Journal

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“…The Cu 2+ centers of CCO are assumed to be one of the causes of the CCO interaction with red and NIR light[10]. However, CCO shows much higher absorption around the 420 and 450nm[11] in the visible range due to the two heme groups a and a3[12]. Blue and green light have shown promises in stem cell differentiation[13] where the effect can be due to light-sensitive ion-channels besides PBM since the transition from glycolysis to oxidative phosphorylation is also a crucial factor in stem cell differentiation.…”

Section: Introductionmentioning

confidence: 99%

Computational modeling of the photon transport, tissue heating, and cytochrome C oxidase absorption during transcranial near-infrared stimulation

Bhattacharya

Dutta

2019

Preprint

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Transcranial near-infrared stimulation (tNIRS) has been proposed as a tool to modulate 1 cortical excitability. However, the underlying mechanisms are not clear where the heating effects on 2 the brain tissue needs investigation due to increased near-infrared (NIR) absorption by water and fat. 3Moreover, the risk of localized heating of tissues (including the skin) during optical stimulation of 4 the brain tissue is a concern. The challenge in estimating localized tissue heating is due to the light 5 interaction with the tissues' constituents, which is dependent on the combination ratio of the scattering 6 and absorption properties of the constituent. Here, apart from tissue heating that can modulate the 7 cortical excitability ("photothermal effects"); the other mechanism reported in the literature is the 8 stimulation of the mitochondria in the cells which are active in the adenosine triphosphate (ATP) 9 synthesis. In the mitochondrial respiratory chain, the complex IV, also named as the cytochrome c 10 oxidase(CCO), is the unit four with three copper atoms. The absorption peaks of CCO are in the visible 11 (420-450nm and 600-700nm) and the near-infrared (760-980nm) spectral region which have been 12 shown to be promising for low level light therapy (LLLT), also known as "photobiomodulation". While 13 much higher CCO absorption peaks in the visible spectrum can be used for the photobiomodulation 14 of the skin, 810nm has been proposed for the non-invasive brain stimulation (using tNIRS) due to the 15 optical window in the NIR spectral region. In this article, we applied a computational approach to 16 delineate the "photothermal effects" from the "photobiomodulation," i.e., to estimate the amount of 17 light absorbed individually by each chromophore in the brain tissue (with constant scattering) and the 18 related tissue heating. Photon migration simulations were performed for motor cortex tNIRS based 19 on a prior work that used a 500mW cm −2 light source placed on the scalp. We simulated photon 20 migration at 630nm and 700nm (red spectral region) and 810nm (near-infrared spectral region). We 21 found a temperature increase in the scalp below 0.25°C and a minimal temperature increase in the 22 gray matter less than 0.04°C at 810nm. Similar heating was found for 630nm and 700nm used for 23 LLLT, so photothermal effects are postulated to be unlikely in the brain tissue. 24

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“…M.c.d. spectra were recorded by using the equipment and techniques described previously (Thomson et al, 1976) and e.p.r. spectra were recorded at approx.…”

Section: Methodsmentioning

confidence: 99%

“…It has, however, been demonstrated initially by e.p.r.t and more recently by m.c.d. studies that, in the normal non-liganded form of the enzyme, the haem of cytochrome a3 is in the high-spin form in both oxidation states Thomson et al, 1976;Babcock et al, 1976). In view of these findings it seemed desirable to investigate the changes occurring in the haem a moiety of an enzyme molecule in which the haem of cytochrome a3 was 'locked' not in the low-spin but in the high-spin form.…”

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confidence: 99%

Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate

Brittain¹,

Greenwood²,

Johnson³

1977

Biochemical Journal

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At neutral pH, formate binds to the haem a3 component of cytochrome c oxidase to give a complex that reacts differently from the non-liganded enzyme with reducing agents. Addition of sodium dithionite to the formate complex leads directly to the formation of the fully reduced species, whereas reduction with ascorbate/tetramethylenephenylene-diamine can lead to the production of a mixed-valence species. The stability of this mixed-valence form was studied, and the species appears to represent a 'steady-state' situation that is stable only in the presence of an excess of O2 and reducing equivalents. Characterization of the mixed-valence complex by electron paramagnetic resonance and magnetic circular dichroism reveals the presence of reduced low-spin haem a together with reduced detectable copper and high-spin ferric haem a3.

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Determination of the heme spin states in cytochrome c oxidase using magnetic circular dichroism

Cited by 32 publications

References 10 publications

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

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

Computational modeling of the photon transport, tissue heating, and cytochrome C oxidase absorption during transcranial near-infrared stimulation

Mixed-valence cytochrome oxidase-formate complex. A steady-state intermediate

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