Chemical Society Seminar: Dr. Gabriela Schlau-Cohen - Single-molecule exploration of the regulation of photosynthetic light harvesting

In photosynthetic light harvesting, absorbed energy migrates through a protein network to reach a dedicated location for conversion to chemical energy. This energy flow is efficient, directional, and, in oxygenic photosynthesis, regulated. The regulatory response, known as non-photochemical quenching (NPQ), involves complex and complicated multi-timescale processes that safely dissipate excess energy, thus protecting the system against deleterious photoproducts. In recent research, a protein within this network, light-harvesting complex stress related (LHCSR), has been implicated in regulation in green algae and moss. However, the mechanisms behind photoprotection that occur in LHCSR remain poorly understood. We explore these mechanisms by probing LHCSR at the single-protein level, enabling us to separate and identify distinct conformations. By characterizing the conformational states and dynamics of individual proteins, we characterize energy dissipation in single LHCSR proteins and how the extent of dissipation changes in response to pH and carotenoid composition, two components known to play a role in photoprotection. From this information, we identify the role of individual complexes in the balance between efficiency and adaptability in photosynthetic light harvesting.