Studies of charge transport through proteins bridged between two electrodes have been the subject of intense research in recent years. However, the complex structure of proteins makes it difficult to elucidate transport mechanisms, and the use of simple peptide oligomers may be an over simplified model of the proteins. To bridge this structural gap, we present here studies of charge transport through artificial parallel coiled-coil proteins conducted in dry environment. Protein monolayers uniaxially oriented at an angle of ∼ 30° with respect to the surface normal were prepared. Current voltage measurements, obtained using conductive-probe atomic force microscopy, revealed the mechano-electronic behavior of the protein films. It was found that the low voltage conductance of the protein monolayer increases linearly with applied force, mainly due to increase in the tip contact area. Negligible compression of the films for loads below 26 nN allowed estimating a tunneling attenuation factor, β(0) , of 0.5-0.6 Å(-1) , which is akin to charge transfer by tunneling mechanism, despite the comparably large charge transport distance. These studies show that mechano-electronic behavior of proteins can shed light on their complex charge transport mechanisms, and on how these mechanisms depend on the detailed structure of the proteins. Such studies may provide insightful information on charge transfer in biological systems.

译文

近年来,通过跨两个电极的蛋白质进行电荷传输的研究一直是研究的重点。但是,蛋白质的复杂结构使得难以阐明转运机制,并且简单肽寡聚物的使用可能是蛋白质的过度简化模型。为了弥合这种结构缺口,我们在这里介绍了在干燥环境中通过人工平行卷曲螺旋蛋白进行电荷传输的研究。制备相对于表面法线单轴取向约30°的蛋白质单分子层。使用导电探针原子力显微镜获得的当前电压测量结果揭示了蛋白质膜的机械电子行为。已经发现,蛋白质单层的低电导率随着施加的力线性增加,这主要是由于尖端接触面积的增加。对于低于26 nN的负载,薄膜的压缩可忽略不计,因此可以估算出隧穿衰减因子β(0)为0.5-0.6Å(-1),尽管电荷传输距离相对较大,但类似于通过隧穿机制进行的电荷转移。这些研究表明,蛋白质的机电行为可以阐明其复杂的电荷传输机制,以及这些机制如何依赖于蛋白质的详细结构。这样的研究可以提供有关生物系统中电荷转移的有见地的信息。

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