Chi Qijin, Farver Ole, Ulstrup Jens
Department of Chemistry and Nano-DTU, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
Proc Natl Acad Sci U S A. 2005 Nov 8;102(45):16203-8. doi: 10.1073/pnas.0508257102. Epub 2005 Oct 31.
A biomimetic long-range electron transfer (ET) system consisting of the blue copper protein azurin, a tunneling barrier bridge, and a gold single-crystal electrode was designed on the basis of molecular wiring self-assembly principles. This system is sufficiently stable and sensitive in a quasi-biological environment, suitable for detailed observations of long-range protein interfacial ET at the nanoscale and single-molecule levels. Because azurin is located at clearly identifiable fixed sites in well controlled orientation, the ET configuration parallels biological ET. The ET is nonadiabatic, and the rate constants display tunneling features with distance-decay factors of 0.83 and 0.91 A(-1) in H(2)O and D(2)O, respectively. Redox-gated tunneling resonance is observed in situ at the single-molecule level by using electrochemical scanning tunneling microscopy, exhibiting an asymmetric dependence on the redox potential. Maximum resonance appears around the equilibrium redox potential of azurin with an on/off current ratio of approximately 9. Simulation analyses, based on a two-step interfacial ET model for the scanning tunneling microscopy redox process, were performed and provide quantitative information for rational understanding of the ET mechanism.
基于分子布线自组装原理，设计了一种由蓝铜蛋白天青蛋白、隧道势垒桥和金单晶电极组成的仿生远程电子转移（ET）系统。该系统在准生物环境中足够稳定且灵敏，适用于在纳米尺度和单分子水平上对远程蛋白质界面电子转移进行详细观察。由于天青蛋白以可控的取向位于明确可识别的固定位点，电子转移构型与生物电子转移相似。电子转移是非绝热的，速率常数在H₂O和D₂O中分别显示出距离衰减因子为0.83和0.91 Å⁻¹的隧道效应特征。通过电化学扫描隧道显微镜在单分子水平原位观察到氧化还原门控隧道共振，表现出对氧化还原电位的不对称依赖性。在天青蛋白的平衡氧化还原电位附近出现最大共振，开/关电流比约为9。基于扫描隧道显微镜氧化还原过程的两步界面电子转移模型进行了模拟分析，为合理理解电子转移机制提供了定量信息。
