Jump to main content
Jump to site search


The dramatic effect of N-methylimidazole on trans axial ligand binding to ferric heme: experiment and theory

Author affiliations

Abstract

The binding energy of CO, O2 and NO to isolated ferric heme, [FeIIIP]+, was studied in the presence and absence of a σ donor (N-methylimidazole and histidine) as the trans axial ligand. This study combines the experimental determination of binding enthalpies by equilibrium measurements in a low temperature ion trap using the van’t Hoff equation and high level DFT calculations. It was found that the presence of N-methylimidazole as the axial ligand on the [FeIIIP]+ porphyrin dramatically weakens the [FeIIIP–ligand]+ bond with an up to sevenfold decrease in binding energy owing to the σ donation by N-methylimidazole to the FeIII(3d) orbitals. This trans σ donor effect is characteristic of ligation to iron in hemes in both ferrous and ferric redox forms; however, to date, this has not been observed for ferric heme.

Graphical abstract: The dramatic effect of N-methylimidazole on trans axial ligand binding to ferric heme: experiment and theory

Back to tab navigation

Supplementary files

Publication details

The article was received on 05 Oct 2018, accepted on 19 Dec 2018 and first published on 20 Dec 2018


Article type: Paper
DOI: 10.1039/C8CP06210B
Citation: Phys. Chem. Chem. Phys., 2019, Advance Article
  •   Request permissions

    The dramatic effect of N-methylimidazole on trans axial ligand binding to ferric heme: experiment and theory

    M. Aarabi, R. Omidyan, S. Soorkia, G. Grégoire, M. Broquier, M. Crestoni, A. de la Lande, B. Soep and N. Shafizadeh, Phys. Chem. Chem. Phys., 2019, Advance Article , DOI: 10.1039/C8CP06210B

Search articles by author

Spotlight

Advertisements