NSF Award
1817448
This project will focus 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 the 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 will support innovations in the science curriculum.<br/><br/><br/>The system that will be studied is PpcA, a 3 heme cytochrome from Geobacter sulfurreducens, genetically modified and covalently labeled with a number of photosensitizers will be used as a model system to study charge transfer reactions. 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 a number of structural techniques. 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 will also facilitate curricular updates in a number of upper level laboratory courses at James Madison University.<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.
