The dynamic structure and function of photosystem II in photosynthesis

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Our research uses a combination of experimental and computational approaches to investigate the primary processes of energy conversion in photosynthesis. Photosynthesis supplies almost all of the energy to all forms of life on Earth. We are following the initial capture of light by photosynthetic pigments, the transfer of the light energy to the photochemical reaction centers (photosystems) and the subsequent transfers of electrons that are used by photosynthesis to ultimately store the energy of light in chemical form. The photosystems which accomplish this task are made of pigment molecules and electron transport co-factors imbedded in a complex of protein subunits. Our unique approach to understanding how energy conversion occurs at a molecular level is to use computers to simulate all of the steps including the dynamic motions of every atom in both the pigments and the proteins. Our protein dynamic models allow us to see how all of the molecules move and interact as the process of energy conversion occurs. The detailed motions of the protein molecules are a key part of how the photosystems manage to hold onto the energy from the absorbed light and convert it with such high efficiency into first electrical energy and then finally chemical energy. We combine our computational approaches with powerful experimental spectroscopic investigations that complement each other. By using the computer simulations to model the experimental data we can understand the molecular origins of reaction center function. Our work focuses on photosystem II, the key enzyme responsible for the splitting of water and evolution of oxygen in photosynthesis. In addition to understanding how this important protein complex functions we are interested in characterizing the many regulatory mechanisms that control its activity and protect it from light induced damage. Our basic research is also important to future development of bio-based photovoltaic devices to produce clean energy.