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.
Laboratoire d'Optique Appliquée, Ecole Polytechnique, ENSTA, INSERM U275, Palaiseau, France.
J W
JW
Petrich
J L
JL
Martin
D
D
Houde
C
C
Poyart
A
A
Orszag
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