Circular dichroism spectra of cytochrome c oxidase

Metallomics ◽  
2011 ◽  
Vol 3 (4) ◽  
pp. 417 ◽  
Author(s):  
Artem V. Dyuba ◽  
Alexander M. Arutyunyan ◽  
Tatiana V. Vygodina ◽  
Natalia V. Azarkina ◽  
Anastasia V. Kalinovich ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Circular Dichroism Spectra ◽  
Circular Dichroïsm

scholarly journals Variable-temperature magnetic-circular-dichroism spectra of cytochrome c oxidase and its derivatives

1977 ◽  
Vol 165 (2) ◽  
pp. 327-336 ◽  
Author(s):  
Andrew J. Thomson ◽  
Thomas Brittain ◽  
Colin Greenwood ◽  
John P. Springall
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
High Spin ◽  
Magnetic Circular Dichroism ◽  
Variable Temperature ◽  
Effect Of Temperature ◽  
Circular Dichroism Spectra ◽  
Circular Dichroïsm ◽  
Magnetic Circular Dichroism Spectra

A detailed study of the effect of temperature on the m.c.d. (magnetic circular dichroism) spectra of cytochrome c oxidase and some of its derivatives was undertaken to characterize the spin states of haem a and a3. The fully reduced enzyme contains haem a32+in its high-spin form and haem a2+in the low-spin state. This conclusion is reached by comparing the spectrum with that of the mixed-valence CO derivatives and its photolysis product. The cyanide derivative of the fully reduced enzyme contains both haem a and a3 in the low-spin ferrous form. The m.c.d. spectra of the fully oxidized derivatives are consistent with the presence of one low-spin ferric haem group, assigned to a, which remains unaltered in the presence of ligands. Haem a3 is high spin in the resting enzyme and the fluoride derivatives, and low spin in the cyanide form. The partially reduced formate and cyanide derivatives have temperature-dependent m.c.d. spectra due to the presence of high- and low-spin haem a33+respectively. Haem a is low-spin ferrous in both. A comparison of the magnitude of the temperature-dependence of haem a33+in the fully oxidized and partially reduced forms shows a marked difference which is tentatively ascribed to the presence of anti-ferromagnetic coupling in the fully oxidized form of the enzyme, and to its absence from the partially reduced derivatives, owing to the reduction of both Cu2+ions.

scholarly journals The nature of haem a3 in the oxidized state of cytochrome c oxidase. Evidence from low-temperature magnetic-circular-dichroism spectroscopy in the near infrared region

1982 ◽  
Vol 207 (1) ◽  
pp. 167-170 ◽  
Author(s):  
A J Thomson ◽  
D G Englinton ◽  
B C Hill ◽  
C Greenwood
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Near Infrared ◽  
Magnetic Circular Dichroism ◽  
Infrared Region ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Near Infrared Region ◽  
Circular Dichroïsm ◽  
Inhibited Enzyme

The magnetic-circular-dichroism (m.c.d.) spectra of oxidized ‘resting’ bovine cytochrome c oxidase and the cyanide-inhibited form are reported at 5.15 T and at 4.2 K along with m.c.d. magnetization curves plotted at selected wavelengths. In both spectra there are features at 790nm and 1564nm due to Cua and haem a respectively, the e.p.r.-detectable components of the enzyme. There is a new peak at 1946nm only in the spectrum of the cyanide-inhibited enzyme. Arguments are advanced that assign this to low-spin ferric haem a3 bridged to Cua3, thereby forming a ferromagnetically coupled pair of metal ions.

scholarly journals The optical properties of CuA in bovine cytochrome c oxidase determined by low-temperature magnetic-circular-dichroism spectroscopy

1983 ◽  
Vol 215 (2) ◽  
pp. 303-316 ◽  
Author(s):  
C Greenwood ◽  
B C Hill ◽  
D Barber ◽  
D G Eglinton ◽  
A J Thomson
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Magnetic Circular Dichroism ◽  
Paramagnetic Species ◽  
Type I ◽  
Magnetization Curves ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Circular Dichroïsm

The visible-near-i.r.-region m.c.d. (magnetic-circular-dichroism) spectrum recorded at low temperature in the range 450-900 nm is reported for oxidized resting mammalian cytochrome c oxidase. M.c.d. magnetization curves determined at different wavelengths reveal the presence of two paramagnetic species. Curves at 576, 613 and 640 nm fit well to those expected for an x,y-polarized haem transition with g values of 3.03, 2.21 and 1.45, i.e. cytochrome a3+. The m.c.d. features at 515, 785 and 817 nm magnetize as a S = 1/2 paramagnet with average g values close to 2, and simulated m.c.d. magnetization curves obtained by using the observed g values of CuA2+, i.e. 2.18, 2.03 and 1.99, fit well to the experimental observations. The form of the m.c.d. magnetization curve at 466 nm is curious, but it can be explained if CuA2+ and cytochrome a3+ contribute with oppositely signed bands at this wavelength. By comparing the m.c.d. spectrum of the enzyme with that of extracted haem a-bisimidazole complex it has been possible to deconvolute the m.c.d. spectrum of CuA2+, which shows transitions throughout the spectral region from 450 to 950 nm. The m.c.d.-spectral properties of CuA2+ were compared with those of a well-defined type I blue copper centre in azurin isolated from Pseudomonas aeruginosa. The absolute intensities of the m.c.d. signals at equal fields and temperatures for CuA2+ are 10-20-fold greater than those for azurin. The optical spectrum of CuA2+ strongly suggests an assignment as a d9 ion rather than Cu(I) bound to a thiyl radical.

scholarly journals Characterization of the partially reduced cyanide-inhibited derivative of cytochrome c oxidase by optical, electron-paramagnetic-resonance and magnetic-circular-dichroism spectroscopy

1981 ◽  
Vol 193 (3) ◽  
pp. 699-708 ◽  
Author(s):  
M K Johnson ◽  
D G Eglinton ◽  
P E Gooding ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Near Infrared ◽  
Magnetic Circular Dichroism ◽  
Circular Dichroism Spectroscopy ◽  
Paramagnetic Resonance ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Circular Dichroïsm ◽  
Reduced State

Optical. e.p.r. and near-infrared low-temperature m.c.d. (magnetic-circular-dichroism) spectroscopy were used to characterize the partially reduced cyanide-inhibited derivative of cytochrome c oxidase produced by anaerobic reductive titration with dithionite. The reductions of cytochrome a3+ and Cu2+a were followed by observation of the e.p.r. signals at g = 3.03, 2.21 and 1.5 and at g = 2.18, 2.03 and 1.99. As reduction proceeds new e.p.r. signals (g = 3.58 and 1.56) appear that quantify to give one haem per enzyme unit when a small excess of dithionite has been titrated in. The e.p.r. signal of the Cu2+a titrates in parallel with the disappearance of the band and 820nm in the optical absorption spectrum. The near-infrared m.c.d. spectrum shows the presence of the low-spin ferric haem, a3+, in the oxidized state of the enzyme, as a well-resolved positive peak at 1650nm. As reduction proceeds this band is replaced by one at 1550nm due to haem a3+(3)–CN in the partially reduced state. Hence as haem a3+(3)–CN becomes e.p.r.-detectable it also shows a near-infrared m.c.d. spectrum characteristic of a low-spin ferric haem. It is concluded that the partially reduced state of cyanide-inhibited cytochrome c oxidase contains a2+ . Cu+a . a3+(3)–CN . Cu+a3.

scholarly journals Circular dichroism of cytochrome c oxidase: Modeling spectra using classical polarizability theory

2010 ◽  
Vol 1797 ◽  
pp. 94-95
Author(s):  
Artem V. Dyuba ◽  
Tatiana V. Vygodina ◽  
Natalia V. Azarkina ◽  
Alexander M. Arutyunyan ◽  
Yury A. Sharonov ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Circular Dichroïsm
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