9404925 Allen The goal of this project is to understand the process by which biological systems can convert light energy into chemical energy with an efficiency near unity. The initial photochemical process in photosynthetic organisms occurs in a pigment-protein complex called the reaction center. The photochemical process is initiated by light absorption that excites a bacteriochlorophyll dimer and starts the transfer of electrons and protons that will be used to generate energy rich compounds. A critical feature of these electron transfer processes is the relationship between the rate and driving force. We propose measuring the process after we have significantly altered the driving force by making specific changes in the energy levels of the bacteriochlorophyll dimer. We plan to use a wide range of techniques ranging from femotosecond transient absorption spectroscopy and electron nuclear paramagnetic resonance spectroscopy to molecular biology. The understanding of the electron transfer processes in this complex should be useful for other biological systems, such as respiratory and electron transfer chains and redox enzymes. %%% The goal of this research is to understand the function of biological systems at a molecular level. Fundamental to all biological processes is the use of energy to create energy rich compounds. These research seeks to understand how biological organisms efficiently convert light into chemical energy. Our approach is to study the complex called the reaction center, that is involved in the initial steps of this conversion process. We alter the complex by use of molecular biology and then apply physical techniques to characterize how the function has changed. More specifically, we make changes that alter the driving force for the reaction and then measure how the rate of the reaction changes. Although the study is applied to a specific complex, we anticipate that the results will be general and applicable to other biological systems. ***
