Amdursky Nadav, Sepunaru Lior, Raichlin Sara, Pecht Israel, Sheves Mordechai, Cahen David
Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel; Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel.
Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel.
Adv Sci (Weinh). 2015 Mar 16;2(4):1400026. doi: 10.1002/advs.201400026. eCollection 2015 Apr.
Electron transfer (ET) proteins are biomolecules with specific functions, selected by evolution. As such they are attractive candidates for use in potential bioelectronic devices. The blue copper protein azurin (Az) is one of the most-studied ET proteins. Traditional spectroscopic, electrochemical, and kinetic methods employed for studying ET to/from the protein's Cu ion have been complemented more recently by studies of electrical conduction through a monolayer of Az in the solid-state, sandwiched between electrodes. As the latter type of measurement does not require involvement of a redox process, it also allows monitoring electronic transport (ETp) via redox-inactive Az-derivatives. Here, results of macroscopic ETp via redox-active and -inactive Az derivatives, i.e., Cu(II) and Cu(I)-Az, apo-Az, Co(II)-Az, Ni(II)-Az, and Zn(II)-Az are reported and compared. It is found that earlier reported temperature independence of ETp via Cu(II)-Az (from 20 K until denaturation) is unique, as ETp via all other derivatives is thermally activated at temperatures >≈200 K. Conduction via Cu(I)-Az shows unexpected temperature dependence >≈200 K, with currents decreasing at positive and increasing at negative bias. Taking all the data together we find a clear compensation effect of Az conduction around the Az denaturation temperature. This compensation can be understood by viewing the Az binding site as an electron trap, unless occupied by Cu(II), as in the native protein, with conduction of the native protein setting the upper transport efficiency limit.
电子转移（ET）蛋白是经过进化选择的具有特定功能的生物分子。因此，它们是潜在生物电子器件中极具吸引力的候选者。蓝色铜蛋白天青蛋白（Az）是研究最多的ET蛋白之一。传统上用于研究蛋白质铜离子的电子转移的光谱学、电化学和动力学方法，最近通过对夹在电极之间的固态单层Az的电导率研究得到了补充。由于后一种测量类型不需要氧化还原过程的参与，它还允许通过氧化还原惰性的Az衍生物监测电子传输（ETp）。在此，报告并比较了通过氧化还原活性和惰性Az衍生物，即Cu（II）和Cu（I）-Az、脱辅基Az、Co（II）-Az、Ni（II）-Az和Zn（II）-Az的宏观ETp结果。研究发现，早期报道的通过Cu（II）-Az的ETp（从20K到变性）与温度无关是独特的，因为通过所有其他衍生物的ETp在温度>≈200K时是热激活的。通过Cu（I）-Az的传导在>≈200K时表现出意想不到的温度依赖性，电流在正偏压下减小，在负偏压下增加。综合所有数据，我们发现在Az变性温度附近Az传导有明显的补偿效应。这种补偿可以通过将Az结合位点视为电子陷阱来理解，除非被Cu（II）占据，就像天然蛋白质中那样，天然蛋白质的传导设定了传输效率的上限。
