Abstract

Two-color picosecond transient Raman spectroscopy is used to study the ultrafast ligand binding reaction of O₂ with hemoglobin. Oxyhemoglobin is photodissociated and the subsequent geminate recombination reaction investigated by vibrational spectroscopy. For ultrafast reaction in solution it is often difficult to separate the dynamics of chemical change from simple relaxation of the internal energy. We have used Stokes and anti-Stokes transient Raman spectroscopy to measure both structural changes in the heme and vibrational energy relaxation. Rates of energy relaxation have been measured in both deoxy and oxyhemoglobin. These results provide detailed information about the coupling between the heme and the protein. For oxyhemoglobin the rate of geminate recombination is faster than the vibrational cooling rate.

© 1991 Optical Society of America