Heme geometry in the 10 K photoproduct from sperm whale carbonmonoxymyoglobin

Antonio Cupane, Eugenio Vitrano, Pal Ormos, G. Ulrich Nienhaus

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

We have measured the Soret band of the photoproduct obtained by complete photolysis of sperm whale carbonmonoxymyoglobin at 10 K. The experimental spectrum has been modeled with an analytical expression that takes into account the homogeneous bandwidth, the coupling of the electronic transition with both high and low frequency vibrational modes, and the effects of static conformational heterogeneity. The comparison with deoxymyoglobin at low temperature reveals three main differences. In the photoproduct, the Soret band is shifted to red. The band is less asymmetric, and an enhanced coupling to the heme vibrational mode at 674 cm-1 is observed. These differences reflect incomplete relaxation of the active site after ligand dissociation. The smaller band asymmetry of the photoproduct can be explained by a smaller displacement of the iron atom from the mean porphyrin plane, in quantitative agreement with the X-ray structure analysis. The enhanced vibrational coupling is attributed to a subtle heme distortion from the planar geometry that is barely detectable in the X-ray structure.

Original languageEnglish
Pages (from-to)111-117
Number of pages7
JournalBiophysical Chemistry
Volume60
Issue number3
DOIs
Publication statusPublished - Jun 11 1996

Keywords

  • Displacement
  • Heme doming
  • Iron out-of-plane
  • Low temperature absorption spectroscopy
  • Photolysis
  • Photolyzed carbonmonoxymyoplobin
  • Vibrational coupling

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Organic Chemistry

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