Intermolecular Coupling in Heme Compounds

Dr. Valeria Starovoitova
Idaho State University
Department of Physics

Nuclear resonance vibrational spectroscopy (NRVS) is a relatively new technique that allows to measure experimental densities of state for Mossbauer nuclei. NRVS can be used to study dynamical properties of heme proteins and heme compounds as soon as they are enriched with Fe57, which is a Mossbauer nucleus. We have utilized NRVS to obtain vibrational densities of state for Fe(II)octaethylporphyrin, Fe(OEP), one of the basic heme compounds. Theoretical VDOS can be calculated using normal mode analysis (NMA) and the resulting force field gave some important information regarding heme dynamics. Single molecule NMA was done previously to refine the vibrational densities of state for several porphyrin compounds. Crystal NMA, calculations that include intermolecular interactions were performed for the first time. Introducing intermolecular coupling resulted in a much better fit to experimental data and clearly demonstrated that crystal calculations were necessary for improved understanding of iron dynamics in heme compounds.