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.