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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Nanosecond electron tunneling between the hemes in cytochrome bo_3
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Nanosecond electron tunneling between the hemes in cytochrome bo_3

机译：细胞色素bo_3中血红素之间的纳秒电子隧穿

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Biological electron transfer (eT) between redox-active cofactors is thought to occur by quantum-mechanical tunneling. However, in many cases the observed rate is limited by other reactions coupled to eT, such as proton transfer, conformational changes, or catalytic chemistry at an active site. A prominent example of this phenomenon is the eT between the heme groups of mitochondrial cytochrome c oxidase, which has been reported to take place in several different time domains. The question of whether pure eT tunneling in the nanosecond regime between the heme groups can be observed has been the subject of some experimental controversy. Here, we report direct observations of eT between the heme groups of the quinol oxidase cytochrome bo_3 from Escherichia coli, where the reaction is initiated by photolysis of carbon monoxide from heme 03. eT from CO-dissociated ferrous heme 03 to the low-spin ferric heme b takes place at a rate of (1.2 ns)~(-1) at 20℃ as determined by optical spectroscopy. These results establish heme-heme electron tunneling in the bo_3 enzyme, a bacterial relative to the mitochondrial cytochrome c oxidase. The properties of eT between the closely lying heme groups in the heme-copper oxidases are discussed in terms of the reorganization energy for the process, and two methods for assessing the rate of electron tunneling are presented.
机译：氧化还原活性辅因子之间的生物电子转移（eT）被认为是通过量子力学隧穿发生的。但是，在许多情况下，观察到的速率受到与eT偶联的其他反应（例如质子转移，构象变化或活性部位的催化化学反应）的限制。这种现象的一个突出例子是线粒体细胞色素C氧化酶血红素基团之间的eT，据报道它发生在几个不同的时域中。是否可以观察到在血红素基团之间的纳秒级纯eT隧穿问题一直是一些实验争论的主题。在这里，我们报道了直接观察到来自大肠杆菌的喹诺醇氧化酶细胞色素bo_3的血红素基团之间的eT，其中反应是通过光解血红素03中的一氧化碳而引发的。eT从CO分离的亚铁血红素03到低旋铁血红素b在20℃下以（1.2 ns）〜（-1）的速率发生，这是通过光谱学确定的。这些结果在bo_3酶中建立了血红素-血红素电子隧穿，bo_3是相对于线粒体细胞色素c氧化酶而言的细菌。根据该过程的重组能，讨论了血红素-铜氧化酶中紧靠的血红素基团之间的eT的性质，并提出了两种评估电子隧穿速率的方法。

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