Effect of 8th Chromophore: A Comprehensive Study of Excitation Energy Transfer in FMO complex

TL;DR

This study investigates how the 8th chromophore influences excitation energy transfer in the FMO complex, revealing that it accelerates energy transfer and enhances relaxation, especially when initial coherence is considered.

Contribution

It provides a comprehensive analysis of the 8th chromophore's role in EET dynamics, highlighting its impact on transfer speed and relaxation in a realistic protein environment.

Findings

Initial coherence accelerates EET compared to mixed states.

Presence of 8th chromophore speeds up relaxation.

8th chromophore enhances overall EET efficiency.

Abstract

The excitation energy transfer (EET) in Fenna-Matthews-Olson (FMO) complex has been investigated in the presence of realistic inhomogeneous protein environment around different bacteriochlorophyll-a (BChla) sites of a 8-site monomer. We studied the effect of initial coherence and the 8th chromophore on the EET dynamics considering relative orientation of transition dipole moments of all the BChla sites. We choose femtosecond coherent laser pulse to prepare initial coherent superposition state. Our non-Markovian simulation reveals that the initial coherence between excited states of BChla sites accelerate the excitation energy transfer process as compared to initial mixed state. Even more impressively, in the presence of the 8th chromophore, the initial pure state relaxes much faster than in the 7-site monomer. Hence the inclusion of 8th chromophore additionally enhances the EET relaxation.