Long-range reactive dynamics in myoglobin

We report the complete vibrational spectrum of the probe nucleus Fe-57 at t he oxygen-binding site of the protein myoglobin. The Fe-pyrrole nitrogen st retching modes of the heme group, identified here, probe asymmetric interac tions with the protein environment. Collective oscillations of the polypept ide, rather than localized heme vibrations, dominate the low frequency regi on. We conclude that the heme "doming" mode is significantly delocalized, s o that distant sites respond to oxygen binding on vibrational time scales. This has ramifications for understanding long-range interactions in biomole cules, such as those that mediate cooperativity in allosteric proteins.