How reduced excitonic coupling enhances light harvesting in the main photosynthetic antennae of diatoms

Significance Photosynthetic energy transfer must remain robust within the disordered protein environment. A high degree of robustness is generally obtained using molecular exciton states, which are excited states delocalized over a few pigments. These states provide several advantages, including a reduced probability of energy trapping in unfavorable sites, which would diminish the energy transfer efficiency. This study combines single-molecule spectroscopy and quantum-mechanical simulations to explore the different strategy of the main light-harvesting complexes of diatoms to enhance robustness. In the absence of strong exciton interactions, the pigment energies are more susceptible to protein structural changes, but the complexes seem to use these fluctuations to switch frequently into low-energy states with improved light-harvesting properties.