Functional control via heme-backbone interactions in respiratory and photosynthetic heme proteins observed with x-ray nuclear absorption spectroscopy

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The ultimate goal of this research project is an understanding of how the biological activity of heme proteins is influenced by the dynamic interaction of the protein backbone with the heme group. Advances in x-ray synchrotron nuclear absorption spectroscopy permit, for the first time, measurement of the heme Fe vibrational density of states under various conditions of oxidation, temperature, ligand configuration, and optical excitation. This detailed dynamic information will be obtained in experiments at the Advanced Photon Source from proteins that span a range of heme-backbone coupling configurations. Comparisons with results from microperoxidase and other truncated versions of heme proteins will help illustrate the non-local heme-backbone interactions. This comprehensive set of vibrational data with then be used to refine the force constants used in non-linear normal mode calculations of heme protein dynamics. This project is jointly supported by the Physics Division in the Mathematical and Physical Sciences Directorate and by the Molecular Biophysics program in the Directorate for Biological Sciences.