TY - JOUR
T1 - Studies on the heme environment of horse heart ferric cytochrome c azide and imidazole complexes of ferric cytochrome c
AU - Ikeda-Saito, Masao
AU - Iizuka, Tetsutaro
N1 - Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 1975/6/26
Y1 - 1975/6/26
N2 - Horse heart ferric cytochrome c was investigated by the following three methods: (I) Light absorption spectrophotometry at 23 °C and 77 °K; (II) Electron paramagnetic resonance (EPR) spectroscopy at 20 °K; (III) Precise equilibrium measurements of ferric cytochrome c with azide and imidazole between 14.43 and 30.90 °C. I and II have demonstrated that: (1) Ferric cytochrome c azide and imidazole complexes were in the purely low spin state between 20 °K and 23 °C; (2) The energy for the three t2g orbitals calculated in one hole formalism shows that azide or imidazole bind to the heme iron in a similar manner to met-hemoglobin azide or imidazole complexes, respectively. III has demonstrated that: (1) The change of standard enthalpy and that of standard entropy were -2.3 kcal/mol and -1.6 cal/mol per degree for the azide complex formation, and -1.4 kcal/mol and 2.9 cal/mol per degree for the imidazole complex formation. (2) A linear relationship between the change of entropy and that of enthalpy was observed for the above data and for the cyanide complex formation. The complex formation of ferric cytochrome c was discussed based on the results of X-ray crystallographic studies compared with hemoglobin and myoglobin.
AB - Horse heart ferric cytochrome c was investigated by the following three methods: (I) Light absorption spectrophotometry at 23 °C and 77 °K; (II) Electron paramagnetic resonance (EPR) spectroscopy at 20 °K; (III) Precise equilibrium measurements of ferric cytochrome c with azide and imidazole between 14.43 and 30.90 °C. I and II have demonstrated that: (1) Ferric cytochrome c azide and imidazole complexes were in the purely low spin state between 20 °K and 23 °C; (2) The energy for the three t2g orbitals calculated in one hole formalism shows that azide or imidazole bind to the heme iron in a similar manner to met-hemoglobin azide or imidazole complexes, respectively. III has demonstrated that: (1) The change of standard enthalpy and that of standard entropy were -2.3 kcal/mol and -1.6 cal/mol per degree for the azide complex formation, and -1.4 kcal/mol and 2.9 cal/mol per degree for the imidazole complex formation. (2) A linear relationship between the change of entropy and that of enthalpy was observed for the above data and for the cyanide complex formation. The complex formation of ferric cytochrome c was discussed based on the results of X-ray crystallographic studies compared with hemoglobin and myoglobin.
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U2 - 10.1016/0005-2795(75)90059-8
DO - 10.1016/0005-2795(75)90059-8
M3 - Article
C2 - 167834
AN - SCOPUS:0016744973
VL - 393
SP - 335
EP - 342
JO - Biochimica et Biophysica Acta - Proteins and Proteomics
JF - Biochimica et Biophysica Acta - Proteins and Proteomics
SN - 1570-9639
IS - 2
ER -