title: Molecular dynamics simulations of cooling in laser-excited heme proteins.
abstract: In transient optical experiments the absorbed photon raises the vibrational temperature of the chromophore. In heme proteins at room temperature conversion of a 530-nm photon into vibrational energy is estimated to raise the temperature of the heme by 500-700 K. Cooling of the heme is expected to occur mainly by interacting with the surrounding protein. We report molecular dynamics simulations for myoglobin and cytochrome c in vacuo that predict that this cooling occurs on the ps time scale. The decay of the vibrational temperature is nonexponential with about 50% loss occurring in 1-4 ps and with the remainder in 20-40 ps. These results predict the presence of nonequilibrium vibrational populations that would introduce ambiguity into the interpretation of transient ps absorption and Raman spectra and influence the kinetics of sub-ns geminate recombination.
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D003574:Cytochrome c Group; D006418:Heme / Q000528:radiation effects*; D006420:Hemeproteins; D007834:Lasers; D009211:Myoglobin; D013696:Temperature; D014732:Vibration
chemical_list: D003574:Cytochrome c Group; D006420:Hemeproteins; D009211:Myoglobin; D006418:Heme