Probing the Role of the Eighth Bacteriochlorophyll in holo-FMO Complex   by Simulated Two-Dimensional Electronic Spectroscopy
  The Fenna-Matthews-Olson (FMO) protein-pigment complex acts as a molecular wire between the outer antenna system and the reaction center (RC); it is an important model system to study the excitonic energy transfer. Recent crystallographic studies report the existence of an additional (eighth) bacteriochlorophyll a (BChl a). To understand the functionality of this eighth BChl, we simulated the two-dimensional electronic spectra of both the 7-site (apo form) and the 8-site (holo form) variant of the FMO complex from green sulfur bacteria, Prosthecochloris aestuarii. By comparing the difference between the spectrum, it was found that the eighth BChl can affect two different excitonic energy transfer pathways, these being: (1) directly involve in the first pathway 6 $\rightarrow$ 3 $\rightarrow$ 1 of the apo form model by passing the excitonic energy to exciton 6; and (2) increase the excitonic wave function overlap between excitons 4 and 5 in the second pathway (7 $\rightarrow$ 4,5 $\rightarrow$ 2 $\rightarrow$ 1) and thus increase the possible downward sampling routes across the BChls. 
Shu-Hao Yeh and Sabre Kais
physics.bio-ph physics.chem-ph