细胞色素c氧化酶功能模型中血红素-超氧化物/Cu(I)中间体的光谱学证据。
Spectroscopic evidence for a heme-superoxide/Cu(I) intermediate in a functional model of cytochrome c oxidase.
作者信息
Collman James P, Sunderland Christopher J, Berg Katja E, Vance Michael A, Solomon Edward I
机构信息
Department of Chemistry, Stanford University, Stanford, CA 94305-5080, USA.
出版信息
J Am Chem Soc. 2003 Jun 4;125(22):6648-9. doi: 10.1021/ja034382v.
A superstructured tetraphenylporphyrin with a covalently attached proximal imidazole axial base and three distal imidazole pickets has been developed as a model for the active site of terminal oxidases such as cytochrome c oxidase. The oxygen adduct of the Fe-only heme (at low temperature) has a diamagnetic NMR and is EPR silent, which taken together with a resonance Raman oxygen isotope sensitive band (nuFe-O) at 575/554 cm-1 (16O2/18O2) indicates formation of a six-coordinate heme-superoxide complex. Unexpectedly, the Fe/Cu complex, where the copper is in a trisimidazole environment approximately 5 A above the heme plane, displays similar characteristics: a diamagnetic NMR, EPR silence, and nuFe-O at 570/544 cm-1. This indicates the dioxygen adduct of this Fe/Cu system is also a superoxide. This contrasts with previously characterized partially reduced dioxygen intermediates of binuclear heme/copper complexes that form Fe/Cu mu-peroxo complexes.
一种具有共价连接的近端咪唑轴向碱基和三个远端咪唑支链的超结构化四苯基卟啉已被开发出来，作为细胞色素c氧化酶等末端氧化酶活性位点的模型。仅含Fe的血红素的氧加合物（在低温下）具有抗磁性核磁共振信号且电子顺磁共振无信号，这与在575/554 cm-1（16O2/18O2）处的共振拉曼氧同位素敏感带（νFe-O）一起表明形成了六配位血红素-超氧化物复合物。出乎意料的是，Fe/Cu复合物（其中铜处于血红素平面上方约5 Å的三咪唑环境中）表现出类似的特征：抗磁性核磁共振信号、电子顺磁共振无信号以及在570/544 cm-1处的νFe-O。这表明该Fe/Cu体系的双氧加合物也是一种超氧化物。这与之前表征的形成Fe/Cu μ-过氧复合物的双核血红素/铜复合物的部分还原双氧中间体形成对比。
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