NSF Award
2216956
This project is focused on understanding the molecular level mechanism of short-range electron transfer in proteins. All living systems obtain energy through electrons occupying high energy states, either through respiratory chains (food) or from light (photosynthesis). Electron transfer is a vital function of the many proteins responsible for storage, transfer, and transformation of this energy. While there is some understanding of the factors controlling charge transfer over longer distances, little is known about biological electron transfer at distances shorter than 1 nm. Filling this gap will advance our knowledge of the fundamental steps in bioenergetics. By developing computational and experimental models to predict and explain the key parameters of these reactions, a cohesive understanding of short-range biological electron transfer will be obtained. In addition, the project will provide research training for undergraduates and underrepresented minority students and will also support innovations in the science curriculum. This project will also facilitate curricular updates in several upper-level laboratory courses at James Madison University. <br/><br/>PpcA, a 3 heme c-type cytochrome from Geobacter sulfurreducens, genetically modified and covalently labeled with several photosensitizers will be used as a model system to study charge transfer reactions. The overarching hypothesis is that tight structural coupling and effective dissipation of excess heat energy are essential to achieve ultrafast charge transfer rates. The kinetics of the reactions will be studied with time-resolved fluorescence and absorbance spectroscopies at room and cryogenic temperatures. The structural integrity of protein-photosensitizer complexes will be monitored with SAXS and CD spectroscopy. Extensive all-atom molecular dynamics simulations will be performed to predict structures and to evaluate structural dynamics. These predictions will be tested experimentally with several structural techniques including nuclear magnetic resonance spectroscopy and x-ray crystallography. The collected kinetic data will be analyzed in the context of molecular structures and will be used to test and revise currently available computational and theoretical approaches for the prediction of electron transfer rates and pathways. This project is funded by the Molecular Biophysics Cluster in the Division of Molecular and Cellular Biosciences.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
