Collaborative Research: Combining Theory and Experiment to Understand Carotenoid Photophysics in Photosynthetic Light-Harvesting

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Carotenoids are essential light-absorbing pigments that help conversion of sunlight energy during photosynthesis and, in addition, provide photoprotection from the sun's damaging effects to photosynthetic organisms. With this award, the Chemistry of Life Processes Program in the Chemistry Division and the Molecular Biophysics Program in the Division of Molecular and Cellular Biosciences is funding Dr. Gascon from University of Connecticut and Dr. Beck from Michigan State University to investigate the energy transfer and photoprotection functions of carotenoids in the proteins of such organisms. High-level computational methods are developed to predict how light harvesting affects the structure of carotenoids within these proteins and experimental methods are used to test these predictions. Results from these studies are applicable to engineering new materials for solar energy capture and storage that are more efficient at absorbing light, while being less susceptible to photodamage. In addition, the project increases the knowledge of high school and undergraduate students, including those from underrepresented groups, on how computational methods help to answer important questions in biology and chemistry, and how computer modeling is prevalent and impacts our daily lives. Carotenoids act as light-harvesting pigments, which are uniquely positioned to absorb light outside the light-capturing range of Chlorophylls (Chl). Equally important is the role of carotenoids as photo-protectors of the photosynthetic apparatus via non-photochemical quenching mechanisms and quenching of singlet oxygen. Two examples of protein complexes with these two capabilities are the peridinin-chlorophyll a-protein (PCP) from marine algae dinoflagellates and the orange carotenoid protein (OCP) from cyanobacteria. Despite the availability of high-resolution structures of PCP, OCP, and other carotenoid-containing light-harvesting proteins, and considerable experimental and theoretical efforts, a general understanding of how the carotenoids function in energy transfer and photoprotection is still not fully available due to longstanding controversies in several areas. This research produces a systematic and synergistic examination of these mechanisms, combining advanced electronic structure calculations in proteins and advanced spectroscopy techniques to discover the controlling spectral factors and the dynamical fate of carotenoids during the first events of light harvesting and photoprotection in photosynthetic proteins.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.