Molecular Dynamics Simulations of Cooling in Laser-Excited Heme Proteins

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 oc...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1986-12, Vol.83 (23), p.8982-8986
Main Authors: Henry, Eric R., Eaton, William A., Hochstrasser, Robin M.
Format: Article
Language:English
Subjects:
Absorption spectra
Atoms
Biological and medical sciences
Biophysical Phenomena
Biophysics
Conformational dynamics in molecular biology
Cooling
Cytochrome c Group
Energy
Fundamental and applied biological sciences. Psychology
Heme - radiation effects
Hemeproteins
Kinetic energy
Kinetics
Lasers
Molecular biophysics
Molecules
Myoglobin
Photons
Porphyrins
Temperature
Vibration
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Summary: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.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.83.23.8982