Optimization of energy transport in the Fenna-Matthews-Olson complex via site-varying pigment-protein interactions

TL;DR

This study investigates how site-specific pigment-protein interactions optimize energy transport in the FMO complex, revealing two main pathways and the roles of coherence and dissipation in efficient exciton transfer.

Contribution

It demonstrates that the FMO complex's interactions are highly optimized and identifies two distinct energy transfer pathways with different dynamical characteristics.

Findings

Two main energy transfer pathways identified

Strong correlation between coherence and efficiency

Challenging assumptions about coupling to the reaction center

Abstract

Energy transport in photosynthetic systems can be tremendously efficient. In particular we study exciton transport in the Fenna-Mathews-Olsen (FMO) complex found in green sulphur bacteria. The exciton dynamics and energy transfer efficiency is dependent upon the interaction with the system environment. Based upon realistic, site-dependent, models of the system-bath coupling, we show that this interaction is highly optimised in the case of FMO. Furthermore we identify two transport pathways and note that one is dominated by coherent dynamics and the other by classical energy dissipation. In particular we note a strong correlation between energy transport efficiency and coherence for exciton transfer from bacteriochlorophyll (BChl) 8 to BChl 4. The existence of two clear pathways and the role played by BChl 4 also challenges assumptions around the coupling of the FMO complex to the reaction centre.