Collaborative Research: De novo Protein Constructs for Photosynthetic Energy Transduction

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With this award, the Chemistry of Life Processes Program in the Division of Chemistry is funding Michael J. Therien (Duke University), Jeffery G. Saven (University of Pennsylvania), and William F. DeGrado (University of California at San Francisco) for research to further the understanding of the precise way plants capture energy from sunlight. Proteins perform many functions in living organisms and catalyze the complex set of chemical reactions necessary for life. Among the most critical of these functions is the conversion of energy from one form to another, such as during photosynthesis, when plants convert sunlight to chemical energy. As a result of this process, tons of carbon dioxide are removed from the atmosphere every year. In this work, the investigators are building artificial proteins that mimic the behavior of proteins in plants involved in photosynthesis. This strategy provides an important means to test how natural photosynthetic proteins work. Important insights can then be used to develop novel proteins that enable energy conversion processes not found in nature. The work will have a broader impact on diverse fields such as biology and energy storage, through the heightened understanding of key molecular events involved in photosynthesis. There is further broad impact on the training of the next generation of scientists. The unique multi-institution structure provides additional opportunities for students of all educational levels, graduate and undergraduate as well as high school, to participate in an exciting collaborative investigation being carried out in three different states.In this research, key protein design principles that provide for photosynthetic energy transduction and storage are being elucidated. An integrated, multi-disciplinary approach is employed toward this goal, and focus is on the evolution of peptide-cofactor complexes that undergo photoinduced charge-transfer reactions, where the protein matrix stabilizes the charge-separated state and guides the efficient separation of electrons and holes. Toward this end: (i) light-harvesting and redox-active cofactors are being designed and synthesized; (ii) de novo proteins are also being designed to selectively bind linked assemblies of these units; (iii) these de novo proteins are then expressed and characterized; (iv) de novo photosynthetic proteins that undergo photo-induced electron transfer are being interrogated using state-of-the-art pump-probe transient optical methods; (v) experimental data is guiding cofactor and protein design and redesign, initially focusing on the positioning of appropriate amino acid side chains near donor and acceptor redox sites to modulate charge separation and charge recombination dynamics; and (vi) the spectroscopic and dynamical properties of re-designed assemblies that control orientation via self-assembly are being characterized as functions of their nanostructured electronic environments. Information from this study is providing new insights into aspects of protein structure and dynamics that are integral for highly efficient photonic energy conversion, pushing the limits of functional de novo design, and guiding the design of complex peptide-cofactor assemblies that have unique photosynthetic functionality.This project is co-funded by the Molecular Biophysics Cluster in the Division of Molecular and Cellular Biosciences and the Computational and Data-Enabled Science and Engineering program.