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
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
复制标题
DOI：
10.1039/c3cp52885e
复制
发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Cahen, David
中科院分区：
文献类型：
--
作者：
Amdursky, Nadav;Ferber, Doron;Cahen, David
将蛋白质集成到分子电子器件中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“传统”蛋白质电子转移（ET）测量不同，跨蛋白质的固态电子转移（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展示了这两种方法之间的根本区别，这允许通过细胞色素 C (Cyt C) 测量 ETp 温度依赖性低至低温，细胞色素 C (Cyt C) 是一种以血红素 (Fe-卟啉) 辅基作为氧化还原中心的 ET 蛋白。我们将 ETp 与电化学 ET 测量进行比较，并对不含 Fe（不含金属卟啉）和不含卟啉的蛋白质进行比较。由于去除卟啉会不可逆地改变蛋白质的构象，因此我们用人血清白蛋白 (HSA) 重复这些测量，并用单一氯化血红素等价物“掺杂”（通过非共价结合），即这些天然和人造蛋白质共享一个共同的修复基团。通过 Cyt C 和 HSA-hemin 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类似 ETp 机制，热激活跳跃（具有类似于 0.1 eV 激活能）> 190 K 和通过超级交换的隧道效应 o190 K。此外，进出 Fe 氧化还原中心的 ET 速率（Fe2+可逆箭头 Fe3+ + e(-)），通过下式测量 HSA-血红素的电化学性能仅比 Cyt C 低 4 倍。然而，虽然从卟啉环中去除 Fe 氧化还原中心会显着影响 ET 速率，但它几乎不会改变通过这些蛋白质的 ETp 电流，而去除大环（从 HSA 中保留其构象）会显着降低 ETp 效率。这些结果表明，跨蛋白质的固态 ETp 不需要氧化还原辅助因子的存在，并且对于 ET，Fe 离子是主要的电子介体，而对于 ETp，卟啉环具有此功能。
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 similar to 0.1 eV activation energy) > 190 K and tunneling by superexchange o190 K. Also, ET rates to and from the Fe redox centres (Fe2+reversible arrow Fe3+ + 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 macrocycle (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.