Dynamics And Reactivity Of Hemoglobin: Nanosecond Time-Resolved Raman Studies

The mechanisms by which structure and structural dynamics modulate reactivity at protein active sites pose one of the fundamental problems of molecular biophysics. During the past decade, it has become increasingly evident that dynamics play an important role in determining the reactivity of heme proteins (1-3). Thus, it is clear that simple determinations of equilibrium structures are often only a first step in addressing this issue. The complexity of the multi-level dynamics of proteins makes it highly desirable to examine systems where both the kinetic rates and the equilibrium structures are very well characterized. In that sense, the ligand binding dynamics of hemoglobins and myoglobins provide a nearly ideal framework in which to explore the biophysical complexities that are at the core of structure-function relationships. The specificity and interpretability of resonance Raman scattering from hemes make it an excellent technique for the structural characterization of the active sites of hemoglobin. Here, we present the results of recent studies in our laboratories utilizing time-resolved resonance Raman spectroscopy that further characterize the structural dynamics occurring at the heme active sites of hemoglobin subsequent to ligand photolysis.