Selective Examination of Heme Protein Azide Ligand-Distal Globin Interactions by Vibrational Circular Dichroism

Richard W. Bormett, Sanford A. Asher, Peter J. Larkin, William G. Gustafson, N. Ragunathan, Teresa B. Freedman, Laurence A. Nafie, Sriram Balasubramanian, Steven G. Boxer, Nai Teng Yu, Klaus Gersonde, Robert W. Noble, Barry A. Springer, Stephen G. Sligar

Research output: Contribution to journalArticlepeer-review


Vibrational circular dichroism (VCD) spectra of the antisymmetric stretch of azide ligated to the heme of a series of evolutionarily diverse and site-directed mutant hemoglobins and myoglobins are anomalously intense and demonstrate an intriguing sensitivity to subtle protein-ligand interactions. The antisymmetric stretch of the azide ligand covalently bound to the low-spin iron shows an anisotropy ratio of -9.5 × 10-4 for sperm whale and horse myoglobin which decreases to -8.0 × 10-4 for human and carp hemoglobin and Chironimus thummi thummi III monomeric hemoglobin. The VCD spectra of these heme-azide complexes depend upon the interactions of the azide ligand with distal heme pocket residues such as the E7 distal histidine and E11 valine. The site-directed mutants of sperm whale (distal histidine substituted Gly E7) and human (distal valine substituted Asn E11) myoglobin have vanishingly small anisotropy ratios (<-0.5 × 10-4), while elephant myoglobin (distal histidine substituted Gin E7) shows an anisotropy ratio of -6.4 × 10-4. The azide ligand ionically bound to a high-spin iron shows a vanishingly small VCD intensity.

Original languageEnglish (US)
Pages (from-to)6864-6867
Number of pages4
JournalJournal of the American Chemical Society
Issue number17
StatePublished - Aug 1 1992

ASJC Scopus subject areas

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


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