As far as I know, the Marcus Theory explains the rates of electron transfers in reactions as a function of differences in free energy between the product/reactant's potential well.
Furthermore, there is the so called inverted region which is often said to be important to explain effects as the photosynthesis. Sadly, I do not see the connection here. The inverted region seems to reduce the transfer rate in the backwards reaction but not in the forwards reaction which creates a net reaction flux. But how can this be explained by the Marcus Theory? I tried to read several sources which claimed to talk about this online, but apparently missed the crucial point.