Researchers at the Indian Institute of Science (IISc) and the California Institute of Technology (Caltech) have investigated the electron flow within Photosystem II (PSII), a crucial component of photosynthesis. Their study, published in the Proceedings of the National Academy of Sciences, addresses the longstanding question of why electrons predominantly flow through the D1 branch of PSII, despite the structural symmetry between the D1 and D2 branches.
Through a combination of molecular dynamics simulations, quantum mechanical calculations, and Marcus theory, the team mapped the energy landscape for electron movement in both branches. They discovered that the D2 branch presents a significantly higher energy barrier, making electron transport energetically unfavorable. Specifically, the transfer of electrons from pheophytin to plastoquinone in the D2 branch requires more activation energy than in the D1 branch, preventing efficient electron flow.
These findings enhance our understanding of natural photosynthesis and may inform the design of efficient artificial photosynthetic systems capable of converting solar energy into chemical fuels, contributing to sustainable renewable energy solutions.