Variable temperature magnetic circular dichroism studies of reduced nitrogenase iron proteins and [4Fe-4S]+ synthetic analog clusters

1993 ◽  
Vol 1164 (2) ◽  
pp. 113-123 ◽  
Author(s):  
Yvonne A. Onate ◽  
Michael G. Finnegan ◽  
Brian J. Hales ◽  
Michael K. Johnson
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Variable Temperature ◽  
Synthetic Analog ◽  
Iron Proteins ◽  
Circular Dichroïsm

scholarly journals pH-dependent forms of the ferryl haem in myoglobin peroxide analysed by variable-temperature magnetic circular dichroism

1989 ◽  
Vol 261 (2) ◽  
pp. 515-522 ◽  
Author(s):  
N Foote ◽  
P M A Gadsby ◽  
C Greenwood ◽  
A J Thomson
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
Variable Temperature ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Zero Field Splitting Parameter ◽  
Varied Temperature ◽  
Splitting Parameter ◽  
Catalytic Cycles ◽  
Circular Dichroïsm

The reaction product of myoglobin and H2O2 exists in two different forms according to the external pH. Varied-temperature magnetic-circular dichroism (m.c.d.) spectroscopy demonstrates that both contain the oxyferryl ion Fe(IV) = O. Alkaline myoglobin peroxide has often been used as a model for oxidized intermediates in the catalytic cycles of haem-containing peroxidases, but absorption and m.c.d. spectra show that the acid form is much more closely related to species such as horeradish peroxidase Compound II. The differences are tentatively ascribed to ionization of the proximal histidine ligand in alkaline myoglobin peroxide. It is also shown that the m.c.d. method allows an estimate of the zero-field splitting parameter of both forms, values of D = 28.0 +/- 3 cm-1 and 35.0 +/- 5 cm-1 being obtained for the alkaline and acid forms respectively.

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