Observation of ultrafast conformational changes in carboxy-myoglobin by time-resolved circular dichroism

A time-resolved circular dichroism experiment is carried out on carboxy-myoglobin. CD is measured with a sub-picosecond time resolution after ligand dissociation. We observe a decrease of the CD signal in a few picoseconds followed by a 100 ps relaxation towards the deoxy-myoglobin values. Thanks to a calculation developed after the polarizability theory, we are able to assign this signal to a global reorganization of the protein conformation