BIOLOGICAL AND BIO-INSPIRED LIGHT-HARVESTING SYSTEMS

In light-harvesting, solar energy is captured and the absorbed energy is transferred through a network of molecules. The photosynthetic light-harvesting machinery uses this process to amplify and regulate solar flux. Our experiments seek to understand the mechanisms in natural systems and control the behavior in synthetic systems.

Energy transfer in photosynthetic light harvesting. Photosynthetic light harvesting is excitonic energy transfer (EET) through a network of antenna proteins, or light-harvesting complexes (LHCs), to reach the reaction center, which occurs with a remarkable near unity quantum efficiency. While it has previously been difficult to maintain the local membrane environment, new biochemical technologies of model membrane systems enable control over membrane area and composition, providing a controlled environment to effectively study EET in the network of LHCs.

J. Ogren, A. Tong, S. Gordon, A. Chenu, Y. Lu, R. Blankenship, J. Cao, G.S. Schlau-Cohen. "Impact of the lipid bilayer on energy transfer kinetics in the photosynthetic protein LH2." Chem Sci, Accepted (2018).

  Free energy landscape of LHCSR1 as a function of two generalized nuclear coordinates.

Free energy landscape of LHCSR1 as a function of two generalized nuclear coordinates.

Photoprotection in photosynthetic light harvesting.  When light absorption exceeds the capacity for utilization by downstream molecular machinery, the excess energy can cause damage. Thus, LHCs have evolved a feedback loop that triggers photoprotective energy dissipation. The crucial importance of photoprotection for plant fitness has been demonstrated, as well as its impact on crop yields. However, the mechanisms of photoprotection - from fast chemical reactions of molecules to slow conformational changes of proteins - have not yet been resolved. We probe both protein dynamics on a millisecond timescale with single-molecule spectroscopy and excited state pathways on a femtosecond timescale with ultrafast spectroscopy.

T. Kondo, A. Pinnola, W. J. Chen, L. Dall’Osto, R. Bassi, G. S. Schlau-Cohen, "Single-Molecule Spectroscopy of LHCSR1 Protein Dynamics Identifies Two Distinct States Responsible for Multi-Timescale Photosynthetic Photoprotection." Nature Chem9, 772 (2017). 

G. S. Schlau-Cohen, J. Berry, “Photosynthetic fluorescence, from molecule to planet.” Physics Today6, 66 (2015).

  DNA-scaffolded molecular aggregates.          

DNA-scaffolded molecular aggregates.

 

 

 

Bio-inspired light harvesting. In parallel to our studies of natural light harvesting, we also focus on bio-inspired light-harvesting systems that use DNA origami to construct nanoscale 3D structures with embedded molecular aggregates. Certain molecular aggregates with optical properties dramatically different from their constituent monomers are promising natural pigment analogs. Using single-molecule and ultrafast spectroscopy we explore how delocalized excited states can be engineered into artificial light-harvesting arrays and balanced with the inherent heterogeneity of bio-inspired materials to improve energy transfer efficiency.

J. L. Banal, T. Kondo, R. Veneziano, M. Bathe, G. S. Schlau-Cohen "Photophysics of J-Aggregate-Mediated Energy Transfer on DNA." J Phys Chem Lett, 8, 5827 (2017).  

Group Members: Toru, Ashley, Minjung, Crystal, Ray, Olivia, Steph