Some Aspects of Electron Transfer in Biological Systems

摘要

Electron transfer occurs over relatively long distances in a variety of systems. In interpreting the measured electron-transfer rates it is usually assumed that the rate constants depend exponentially on the distance separating the two redox sites and that this distance dependence arises from the decrease in the electronic coupling of the redox sites with increasing separation. Although the electronic coupling is an important factor determining the distance dependence of the rate, theoretical considerations show that the nuclear factors are also important. Another factor, of particular importance in biological systems, is the accessibility of different protein conformations. Such conformation changes afford a mechanism for controlling electron-transfer rates and can lead to directional electron transfer under suitable conditions. The effects of conformation changes can be particularly marked, and even unexpected, in the inverted free-energy region. 22 refs., 9 figs., 1 tab. (ERA citation 14:029433)