Low-temperature magnetic circular dichroism studies of the photoreaction of horseradish peroxidase compound I

Biochemistry ◽  
1988 ◽  
Vol 27 (7) ◽  
pp. 2503-2509 ◽  
Author(s):  
Zbigniew Gasyna ◽  
William R. Browett ◽  
Martin J. Stillman
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Horseradish Peroxidase ◽  
Magnetic Circular Dichroism ◽  
Compound I ◽  
Circular Dichroïsm

scholarly journals Low-temperature studies on mixed-valence cytochrome oxidase by using magnetic circular dichroism

1976 ◽  
Vol 159 (3) ◽  
pp. 811-813 ◽  
Author(s):  
T Brittain ◽  
J Springall ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Cytochrome Oxidase ◽  
High Spin ◽  
Room Temperature ◽  
Magnetic Circular Dichroism ◽  
Mixed Valence ◽  
Spin States ◽  
High Spin States ◽  
Circular Dichroïsm

The spin states of the haem components of mixed-valence cytochrome oxidase were studied at room temperature and at temperature down to 20K by using magnetic circular dichroism. The room-temperature studies show the presence of a low-spin ferrous haem together with a low-spin ferric haem, which we attribute to heams a3 and a respectively. At temperatures below 100K it appears that the CO of the mixed-valence CO complex may be irreversibly photolysed, and that in this case haems a and a3 assume their high-spin states. Thus in this enzyme haem-haem interactions appear possible at temperatures below 100K.

The three-iron cluster in a ferredoxin from Desulphovibrio gigas A low-temperature magnetic circular dichroism study

1981 ◽  
Vol 670 (1) ◽  
pp. 93-100 ◽  
Author(s):  
Andrew J. Thomson ◽  
A.Edward Robinson ◽  
Michael K. Johnson ◽  
Jose J.G. Moura ◽  
Isobel Moura ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Low Temperature ◽  
Magnetic Circular Dichroism ◽  
Iron Cluster ◽  
Circular Dichroïsm

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.

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