Beratan David N
Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708, USA; email:
Department of Biochemistry, Duke University, Durham, North Carolina 27710, USA.
Annu Rev Phys Chem. 2019 Jun 14;70:71-97. doi: 10.1146/annurev-physchem-042018-052353. Epub 2019 Feb 6.
The corpus of electron transfer (ET) theory provides considerable power to describe the kinetics and dynamics of electron flow at the nanoscale. How is it, then, that nucleic acid (NA) ET continues to surprise, while protein-mediated ET is relatively free of mechanistic bombshells? I suggest that this difference originates in the distinct electronic energy landscapes for the two classes of reactions. In proteins, the donor/acceptor-to-bridge energy gap is typically several-fold larger than in NAs. NA ET can access tunneling, hopping, and resonant transport among the bases, and fluctuations can enable switching among mechanisms; protein ET is restricted to tunneling among redox active cofactors and, under strongly oxidizing conditions, a few privileged amino acid side chains. This review aims to provide conceptual unity to DNA and protein ET reaction mechanisms. The establishment of a unified mechanistic framework enabled the successful design of NA experiments that switch electronic coherence effects on and off for ET processes on a length scale of multiple nanometers and promises to provide inroads to directing and detecting charge flow in soft-wet matter.
电子转移（ET）理论体系为描述纳米尺度下电子流动的动力学和动态过程提供了强大的能力。那么，核酸（NA）电子转移为何仍不断带来惊喜，而蛋白质介导的电子转移却相对较少出现机制上的重大突破呢？我认为这种差异源于两类反应截然不同的电子能量格局。在蛋白质中，供体/受体与桥之间的能隙通常比在核酸中要大几倍。核酸电子转移可以在碱基之间进行隧穿、跳跃和共振传输，并且涨落能够促使机制之间的转换；蛋白质电子转移则局限于氧化还原活性辅因子之间的隧穿，以及在强氧化条件下少数几个特殊氨基酸侧链之间的隧穿。本综述旨在为DNA和蛋白质电子转移反应机制提供概念上的统一。统一机制框架的建立使得成功设计出核酸实验成为可能，这些实验能够在多个纳米的长度尺度上对电子转移过程开启和关闭电子相干效应，并有望为在软湿物质中引导和检测电荷流动提供途径。
