Picosecond time-resolved resonance Raman studies of hemoglobin: Implications for reactivity

E. W. Findsen, J. M. Friedman, M. R. Ondrias, S. R. Simon

Research output: Contribution to journalArticle

76 Scopus citations

Abstract

Picosecond time-resolved Raman spectra of hemoglobin generated with blue pulses (20 to 30 picoseconds) that were resonant with the Soret band and of sufficient intensity to completely photodissociate the starting liganded sample are reported. For both R- and T-state liganded hemoglobins, the peak frequencies in the spectrum of the deoxy transient were the same at approximately 25 picoseconds as those observed at 10 nanoseconds subsequent to photodissociation. In particular, the large R-T differences in the frequency of the stretching mode for the iron-proximal histidine bond (νFe-His) detected in previously reported nanosecond-resolved spectra were also evident in the picosecond-resolved spectra. The implications of this finding with respect to the distribution of strain energy in the liganded protein and the origin of the time course for geminate recombination are discussed. On the basis of these results, a microscopic model is proposed in which delocalization of strain energy is strongly coupled to the coordinate of the iron. The model is used to explain the origin of the R-T differences in the rates of ligand dissociation.

Original languageEnglish (US)
Pages (from-to)661-665
Number of pages5
JournalScience
Volume229
Issue number4714
DOIs
StatePublished - 1985

ASJC Scopus subject areas

  • General

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