2024-2025 Kavli Heising-Simons Junior Fellow
Faculty Advisor: Professor Graham Fleming
Johanna Hall is a third-year chemistry PhD student in the Fleming group, where she studies energy transfer dynamics of natural and artificial photosynthetic systems. Johanna grew up in Georgia and received a B.S. in environmental engineering from Georgia Tech in 2022. She worked in the Environmental Microbial Genomics Laboratory at Georgia Tech before coming to Berkeley.
Johanna’s research aims to uncover new details of photosynthetic efficiency by investigating the light harvesting complex II (LHCII) of plant photosystems. Non-photochemical quenching (NPQ) processes dissipate excess absorbed light energy as heat and primarily act in LHCII. To uncover molecular details of NPQ, Johanna plans to use two-dimensional electronic-vibrational (2DEV) spectroscopy, which provides improved spectral resolution from other techniques with its complementary axes of information; the visible pump pulses provide information on the electronic energy states of a molecule while the infrared probe pulse reports on the local environment surrounding a molecule, which also enables correlation of dynamical information to physical sites in the system. With 2DEV, Johanna will characterize a variety of mutated LHCII trimers with specific chlorophyll molecules removed to determine how each molecule impacts the energy transfer dynamics. Then, she will use LHCII trimer samples with xanthophylls, carotenoid molecules essential for NPQ, to determine the interaction between xanthophylls and chlorophylls. 2DEV can provide insight into this through detection of excited state vibration signals in chlorophylls and carotenoids. This research will provide crucial insight to facilitate the design of NPQ-analogous feedback mechanisms in artificial solar energy systems to maintain efficiency and sustainability of these technologies. Johanna will also collaborate with Professor David Limmer to determine the role of entropy and enthalpy in driving energy transfer dynamics in photosynthesis. With Limmer, Johanna will also create a model system to better understand how entropic effects are controlled by system components and how these may be altered to tune entropy,