Vibrational energy relaxation processes in heme proteins

Vibrational energy relaxation pathways from optically excited heme proteins are studied using a transient thermal phase grating technique which monitors the solvent lattice temperature. Vibrational energy transfer from the porphyrin ring to the protein backbone leads to extensive delocalization of the energy in the protein helix which is efficiently transferred to the water interface in less than 20 psec. A slower relaxation process on the nanosecond time scale is also observed. The slow relaxation processes of high potential energy states of the heme proteins accessed during the high internal energy conditions of the optically excited molecule.