Site-Dependent Fluctuations Optimize Electronic Energy Transfer in the Fenna–Matthews–Olson Protein

Abstract

Light absorbed by light-harvesting antennae is transferred to the reaction center (RC). The excitation energy transfer (EET) to the RC is known to proceed with nearly perfect quantum yield. However, understanding of EET is still limited at the molecular level. Here, we examine the dynamics in the Fenna−Matthews−Olson (FMO) protein by developing an efficient molecular dynamics simulation that can properly describe the electronic properties of bacteriochlorophylls. We find that the FMO protein consists of sites with heterogeneous fluctuations extending from fast to slow modulation. We also find that efficient EETs are facilitated by site-dependent fluctuations that enhance the resonance condition between neighboring sites with large site energy differences and circumvent exciton trapping on the pathway to the RC. Knowledge of site-dependent fluctuations is an important component of understanding optimization of EET in photosynthetic systems.

Stochastic collision model approach to transport phenomena in quantum networks

“…Specifically, transport efficiency is optimized when certain nodes are subjected to strong noise, while the others to very low levels. Remarkably, these two communities are consistent, to a high degree, with the recent discovery of two classes of site-dependent fluctuations in the FMO complex [15].…”

Anomalous Temperature Dependence of Exciton Spectral Diffusion in Tetracene Thin Film

“…We note that the significant acceleration of the spectral diffusion with temperature has not been observed in other molecular systems. A recent 2DES study on chlorosomes has reported that the correlation time Λ −1 is almost the same between 77 and 300 K; 50 in a recent molecular dynamics simulation on the exciton dynamics in light-harvesting antennae, Λ does not vary by more than a factor of 2 between 77 and 300 K. 51 This is reasonable, because the correlation time is determined by the spectral density of the phonon bath that, in general, does not change significantly with temperature.…”

Predictive First-Principles Modeling of a Photosynthetic Antenna Protein: The Fenna–Matthews–Olson Complex

“…The Fenna–Matthews–Olson (FMO) pigment–protein complex, found in green sulfur bacteria, is one of the most thoroughly studied photosynthetic proteins (see Figure ). − The primary function of FMO is to transfer the excitation energy from a much larger chlorosome antenna to the intramembrane reaction center complex, where electronic excitation initiates charge transfer process.…”

“…This approach results in a significant ambiguity in determination of BChl a site energies and typically does not account for environment-driven variations in transition dipole moments of individual pigments and interpigment couplings. While molecular modeling based on structural data could provide unambiguous assignment of excitonic interactions and energy flow in FMO, internal complexity of the system and necessity to sample protein degrees of freedom and accurately describe electronic structure and couplings between BChl pigments and vibronic interactions between pigments and the protein environment makes this task challenging. ,,− ,,,,,− …”