Magnetic circular dichroism of symmetry and spin forbidden transitions of high-spin metal ions

2000 ◽  
Vol 113 (12) ◽  
pp. 5003 ◽  
Author(s):  
Vasily S. Oganesyan ◽  
Andrew J. Thomson
Keyword(s):  
Circular Dichroism ◽  
Metal Ions ◽  
High Spin ◽  
Magnetic Circular Dichroism ◽  
Forbidden Transitions ◽  
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.

scholarly journals Magnetization curves of haemoproteins measured by low-temperature magnetic-circular-dichroism spectroscopy

1980 ◽  
Vol 191 (2) ◽  
pp. 411-420 ◽  
Author(s):  
A J Thomson ◽  
M K Johnson
Keyword(s):  
Circular Dichroism ◽  
Cytochrome C ◽  
High Spin ◽  
Ground State ◽  
Magnetic Circular Dichroism ◽  
Striking Difference ◽  
Zero Field ◽  
Magnetization Curves ◽  
Horse Heart Cytochrome ◽  
Circular Dichroïsm

The magnetic-circular-dichroism (m.c.d.) spectra of methymyoglobin cyanide and oxidized horse heart cytochrome c were measured in the region of the Soret band over a range of temperatures from 1.5 to 50 K and in fields from 0 to 5T. A similar study has been made with reduced bovine heart cytochrome c oxidase, which contains one high-spin ferrous haem, namely a3. M.c.d. magnetization curves characteristic of an isolated Kramer's ground state with spin S = 1/2. These curves contrast with the magnetization curve of the high-spin ferrous haem with spin S = 2. The electronic ground state of the latter compound contains zero-field components that are thermally accessible over the temperature range of the experiment. Hence the magnetization curves are a complex nested set. The magnetization curves of the S = 1/2 proteins were analysed and it is shown that it is possible to make estimates of the ground-state g-factors even in the presence of rhombic anisotropy, provided that some knowledge of the polarizations of the electronic transitions is available. The striking difference between the m.c.d. magnetization curves of a simple S = 1/2 paramagnet and magnetically complex ground state should prove extremely useful when m.c.d. spectroscopy is sued to probe the magentic properties of metal centres in proteins, and should have wide application beyond the field of haemoproteins.

Conformational Transitions of Ferricytochrome c in Strong Inorganic Acids

2006 ◽  
Vol 71 (11-12) ◽  
pp. 1627-1641 ◽  
Author(s):  
Marek Stupák ◽  
Jaroslava Bágeľová ◽  
Diana Fedunová ◽  
Marián Antalík
Keyword(s):  
Circular Dichroism ◽  
High Spin ◽  
Low Temperatures ◽  
Magnetic Circular Dichroism ◽  
High Spin State ◽  
Conformational Transitions ◽  
Optical Absorption Spectroscopy ◽  
Spin States ◽  
Inorganic Acids ◽  
Circular Dichroïsm

Conformational transitions of horse heart ferricytochrome c (ferricyt c) have been investigated in the presence of strong inorganic acids and their salts by optical absorption spectroscopy, magnetic circular dichroism and circular dichroism. In the presence of acids (HClO4 or H2SO4, pH 2) or their salts (1 M NaClO4 or Na2SO4, pH 2, 25 °C), the three ligation states of ferricyt c heme were identified. One is the high-spin state: His18-Fe-H2O (40-50%), and two are the low-spin states: His18-Fe-Met80 (30-25%) and His18-Fe-His (30-25%). Under these conditions low temperatures facilitate native heme coordination of ferricyt c. Transition from low-spin to high-spin heme coordination of ferricyt c is complete in 1 M HClO4 or 3 M H2SO4. At the concentration of HClO4 and H2SO4 above 3 M, different behavior in spectral transitions of ferricyt c near the heme is observed. High-spin pentacoordinated ferricyt c with the heme ligand of His18-Fe is formed in 8 M H2SO4. This state is unstable at higher concentration of H2SO4 and porphyrin ferricyt c is formed. At HClO4 concentration higher than 3 M, the new, until this time not observed heme coordination structure of ferricyt c originates.

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