Large scale FRET simulations reveal the control parameters of phycobilisome light harvesting complexes

TL;DR

This study uses large-scale FRET simulations to identify key control parameters of phycobilisome light harvesting complexes, revealing their robustness and efficiency in energy transfer despite structural variations.

Contribution

The paper introduces a comprehensive dynamic Hamiltonian model to simulate energy transfer in PBS, highlighting the network's robustness and the influence of structural parameters.

Findings

Energy transfer is robust to distance and angle variations.

The chromophore network enhances energy distribution across the PBS.

PBS provides flexible and efficient light harvesting in aquatic photosynthesis.

Abstract

Phycobilisomes (PBS) are massive structures that absorb and transfer light energy to photochemical reaction centers. Among the range of light harvesting systems, PBS are considered to be excellent solutions for absorption cross-sections but relatively inefficient energy transferring systems. This is due to the combination of a large number of chromophores with intermediate coupling distances. Nevertheless, PBS systems persisted from the origin of oxygenic photosynthesis to present day cyanobacteria and red algae, organisms that account for approximately half of the primary productivity in the ocean. In this study we modeled energy transfer through subsets of PBS structures, using a comprehensive dynamic Hamiltonian model. Our approach was applied, initially, to pairs of phycobilin hexamers and then extended to short rods. By manipulating the distances and angles between the structures we could probe the dynamics of exciton transfer. These simulations suggest that the PBS chromophore network enhances energy distribution over the entire PBS structure, both horizontally and vertically to the rod axis. Furthermore, energy transfer was found to be relatively immune to the effects of distances or rotations, within the range of intermediate coupling distances. Therefore, we suggest that the PBS provides unique advantages and flexibility to aquatic photosynthesis.