Efficient Energy Transfer in Light-Harvesting Systems, III: The Influence of the Eighth Bacteriochlorophyll on the Dynamics and Efficiency in FMO

The most recent crystal structure of the Fenna–Matthews–Olson (FMO) protein complex indicates the presence of an additional eighth chromophore, which has been proposed to serve as a link between the chlorosome and the remaining seven chromophores. Here, we investigate the implications of this scenario through numerical calculations with the generalized Bloch–Redfield (GBR) equation and the noninteracting blip approximation (NIBA). It is shown that the oscillations often observed in the population relaxation of sites 1 and 2 may be completely suppressed in the eight-site model due to the initial preparation. Second it is demonstrated that while the presence of the eighth chromophore does not cause a dramatic change in the energy-transfer efficiency, it does however lead to a dominant energy-transfer pathway that can be characterized by an effective three-site system. Finally, we confirm that the energy-transfer process in the eight-site complex remains efficient and robust through computations of the optimal values of the bath parameters.