Dynamics of cyanide binding to ferrous Scapharca inaequivalvis homodimeric hemoglobin

Alberto Boffi, Emilia Chiancone, Eric S. Peterson, Jiaqian Wang, Denis L. Rousseau, Joel M. Friedman

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Flash photolysis experiments have been carded out for the first time on a hemoglobin ferrous cyanide adduct with an 8 ns laser pulse. A 95% nonexponential rebinding process occurs within 2 μs after full photolysis in ferrous cyanide dimeric Scapharca inaequivalvis hemoglobin (HbI), indicating that once photolyzed the cyanide anion is not able to escape from the protein matrix and rebinds to the heme iron. The resonance Raman spectrum of the 10 ns photoproduct is identical to that of the fully relaxed deoxy derivative, indicating that in the ferrous cyanide HbI adduct protein relaxation occurs within 10 ns after photolysis. This behavior is at variance with that of the carbonmonoxy HbI derivative in which very little geminate rebinding is observed and the photoproduct relaxes with a lifetime of 1 μs. The fast relaxation of the cyanide HbI photoproduct can be accounted for by the small perturbation of the heme structure induced by cyanide binding to ferrous HbI. This is consistent with a deoxy-like conformation of the HbI ferrous cyanide adduct and implies that the pathway for relaxation involves only minor local rearrangements of the heme moiety. Photolysis experiments carded out on ferrous cyanide horse myoglobin, which can be saturated only partially, show a qualitatively similar behavior in ligand rebinding, indicating that the geminate process of the cyanide anion is a general phenomenon in hemoproteins.

Original languageEnglish (US)
Pages (from-to)4510-4514
Number of pages5
Issue number15
StatePublished - Apr 15 1997

ASJC Scopus subject areas

  • Biochemistry


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