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首页> 外文期刊>Physical chemistry chemical physics: PCCP >Redox activity distinguishes solid-state electron transport from solution-based electron transfer in a natural and artificial protein: cytochrome C and hemin-doped human serum albumin
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Redox activity distinguishes solid-state electron transport from solution-based electron transfer in a natural and artificial protein: cytochrome C and hemin-doped human serum albumin

机译：氧化还原活性将固态电子传递与基于溶液的电子传递区别于天然和人工蛋白质：细胞色素C和血红素掺杂的人血清白蛋白

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Integrating proteins in molecular electronic devices requires control over their solid-state electronic transport behavior. Unlike "traditional" electron transfer (ET) measurements of proteins that involve liquid environments and a redox cycle, no redox cofactor is needed for solid-state electron transport (ETp) across the protein. Here we show the fundamental difference between these two approaches by macroscopic area measurements, which allow measuring ETp temperature dependence down to cryogenic temperatures, via cytochrome C (Cyt C), an ET protein with a heme (Fe-porphyrin) prosthetic group as a redox centre. We compare the ETp to electrochemical ET measurements, and do so also for the protein without the Fe (with metal-free porphyrin) and without porphyrin. As removing the porphyrin irreversibly alters the protein's conformation, we repeat these measurements with human serum albumin (HSA), 'doped' (by non-covalent binding) with a single hemin equivalent, i.e., these natural and artificial proteins share a common prosthetic group. ETp via Cyt C and HSA-hemin are very similar in terms of current magnitude and temperature dependence, which suggests similar ETp mechanisms via these two systems, thermally activated hopping (with ~0.1 eV activation energy) >190 K and tunneling by superexchange <190 K. Also, ET rates to and from the Fe redox centres (Fe~(2+) Fe~(3+) + e~-), measured by electrochemistry of HSA-hemin are only 4 times lower than those for Cyt C. However, while removing the Fe redox centre from the porphyrin ring markedly affects the ET rate, it hardly changes the ETp currents through these proteins, while removing the macro-cycle (from HSA, which retains its conformation) significantly reduces ETp efficiency. These results show that solid-state ETp across proteins does not require the presence of a redox cofactor, and that while for ET the Fe ion is the main electron mediator, for ETp the porphyrin ring has this function.
机译：在分子电子设备中整合蛋白质需要控制其固态电子传输行为。与涉及液体环境和氧化还原循环的蛋白质的“传统”电子转移（ET）测量不同，跨蛋白质的固态电子传输（ETp）不需要氧化还原辅助因子。在这里，我们通过宏观区域测量显示了这两种方法之间的根本区别，这可以通过细胞色素C（Cyt C）（一种带有血红素（铁卟啉）的辅基作为氧化还原蛋白的ET蛋白）来测量低至低温的ETp温度依赖性。中央。我们将ETp与电化学ET测量进行了比较，并且对没有Fe（具有无金属卟啉）和没有卟啉的蛋白质也进行了比较。由于去除卟啉会不可逆地改变蛋白质的构象，因此我们使用人类血白蛋白（HSA）重复这些测量，并以单个血红素当量“掺杂”（通过非共价结合），即这些天然和人工蛋白质共享相同的义肢基团。通过Cyt C和HSA-hemin产生的ETp在电流大小和温度依赖性方面非常相似，这表明通过这两个系统的ETp机制相似，即热激活跳跃（具有〜0.1 eV激活能量）> 190 K，超交换隧穿<190同样，通过HSA-hemin的电化学测量，去往和来自Fe氧化还原中心的ET率（Fe〜（2+）Fe〜（3+）+ e〜-）仅比Cyt C低4倍。但是，虽然从卟啉环上去除Fe氧化还原中心显着影响ET速率，但几乎不改变通过这些蛋白质的ETp电流，同时去除大环（从保留其构象的HSA中）则大大降低了ETp效率。这些结果表明，跨蛋白质的固态ETp不需要氧化还原辅因子的存在，而对于ET，Fe离子是主要的电子介质，对于ETp，卟啉环具有此功能。

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