Modeling incoherent exciton transport between chlorosome tubes

Chlorosomes are the antennae of the efficient light harvesting complex in green (non-sulfur) bacteria. The ultrafast energy transfer process in natural light harvesting systems can be understood in terms of exciton transport. In chlorosomes, excitons can be delocalized over hundreds of molecules, making it of eminent interest to study large model systems composed of many (thousands) of molecules that are large enough to describe the exciton dynamics that occur in vivo in chlorosomes. In this study, we examine a recently developed Frenkel exciton Hamiltonian of a three coaxial tube chlorosome model based on an all-atom molecular dynamics simulation. We use the computationally efficient time domain Förster resonant energy transfer method to find the timescales of incoherent transfer between the chlorosome walls in this large model. We found that the population transfer rate between neighboring chlorosome walls is ∼2.3 ps-1. We used three different choices of initial quantum states for these transfer processes and found that this transfer timescale between neighboring walls does not vary significantly for these.