Ikeda-Saito M, Iizuka T
Biochim Biophys Acta. 1975 Jun 26;393(2):335-42. doi: 10.1016/0005-2795(75)90059-8.
Horse heart ferric cytochrome c was investigated by the following three methods: (I) Light absorption spectrophotometry at 23 degrees C and 77 degrees K; (II) Electron paramagnetic resonance (EPR) spectroscopy at 20 degrees K; (III) Precise equilibrium measurements of ferric cytochrome c with azide and imidazole between 14.43 and 30.90 degrees C. I and II have demonstrated that: (1) Ferric cytochrome c azide and imidazole complexes were in the purely low spin state between 20 degrees K and 23 degrees 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 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.
采用以下三种方法对马心铁细胞色素c进行了研究：（I）在23℃和77K下进行光吸收分光光度法；（II）在20K下进行电子顺磁共振（EPR）光谱法；（III）在14.43至30.90℃之间对铁细胞色素c与叠氮化物和咪唑进行精确的平衡测量。I和II已证明：（1）在20K至23℃之间，铁细胞色素c叠氮化物和咪唑配合物处于纯低自旋态；（2）用单空穴形式计算的三个t2g轨道的能量表明，叠氮化物或咪唑分别以与高铁血红蛋白叠氮化物或咪唑配合物类似的方式与血红素铁结合。III已证明：（1）叠氮化物配合物形成的标准焓变和标准熵变分别为-2.3 kcal/mol和-1.6 cal/mol·度，咪唑配合物形成的标准焓变和标准熵变分别为-1.4 kcal/mol和2.9 cal/mol·度。（2）对于上述氰化物配合物形成的数据，观察到熵变和焓变之间存在线性关系。结合血红蛋白和肌红蛋白的X射线晶体学研究结果，对铁细胞色素c的配合物形成进行了讨论。
