Time-resolved Raman spectroscopy with subpicosecond resolution: vibrational cooling and delocalization of strain energy in photodissociated (carbonmonoxy)hemoglobin.
A Raman spectrometer that provides both subpicosecond resolution and independent, tunable pump and probe pulses is described. The spectrometer is employed to obtain time-resolved spectra of (carbonmonoxy)hemoglobin (HbCO) at times from 0.2 to 95 ps subsequent to ligand photodissociation. The spectra are interpreted in terms of a vibrationally hot heme that cools substantially in 10 ps. Concomitant with the proposed vibrational cooling is a slower relaxation, which we suggest results from a protein response to heme doming induced by ligand detachment. Results and interpretations are discussed in the context of current models of the heme photophysics and of hemoglobin reactivity.
Petrich
J W
JW
Laboratoire d'Optique Appliquée, Ecole Polytechnique, ENSTA, INSERM U275, Palaiseau, France.
Martin
J L
JL
Houde
D
D
Poyart
C
C
Orszag
A
A
D000328:Adult; D002263:Carboxyhemoglobin / Q000378:metabolism / Q000528:radiation effects*; D006441:Hemoglobin A / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D007834:Lasers; D008024:Ligands; D010782:Photolysis; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman / Q000379:methods; D013997:Time Factors
D008024:Ligands; D006441:Hemoglobin A; D002263:Carboxyhemoglobin