Long-Range Triplet-Triplet Energy Transfer within Metal-Substituted Hemoglobins

Haya Zemel, Brian M Hoffman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

71 Scopus citations


We present a detailed analysis of the long-range (Forster-type) triplet-to-triplet energy transfer between the photoexcited triplet states of the zinc and magnesium protoporphyrin IX chromophores of Zn- and Mg-substituted hemoglobin. The observations of this rarely detected process are made in fluid solution and at ambient temperature by monitoring the time dependence of triplet-triplet absorption subsequent to flash excitation. This appears to be the first time that rate constants have been measured for Forster energy transfer (triplet) between chromophores at crystallographically known distances and orientations. To provide further reference data on chromophore-protein complexes, we have measured the triplet decay rates for zinc myoglobin (k1 = 70 ± 5 s-1) and magnesium myoglobin (k = 24 ± 1 s-1) and the bimolecular rate constant for quenching the zinc myoglobin triplet by 02 (k1 = 1.25 X 108 m-1 s-1) and by dithionite (kq = 2.4 X 106 m-1 s-1).

Original languageEnglish (US)
Pages (from-to)1192-1201
Number of pages10
JournalJournal of the American Chemical Society
Issue number5
StatePublished - Jan 1 1981

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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