Possible Interaction: Imidazole and Ferric Ion

“This large value is considered evidence for a weakened sigma bond between the proximal imidazole and ferric iron in this form, and for a feature contributing to the origin of the high spin-low spin equilibrium exhibited by MbN3 [Beetlestone, J., & George, P. (1964) Biochemistry 5, 707-714].”

“The imidazole can be displaced in the ferric protein by cyanide, guanidine, or by an amine, analogous to its displacement by CO or NO in the ferrous protein.”

“ Fe++ and a number of other heavy metal ions, as well as dipyridyl, lipoic acid, CoA—SH, and H2O2 generated in situ strongly inhibit it, whereas ascorbic acid, imidazole , aminopterin, and folic acid have little or no effect.”

“The pKa of the imidazole also decides the extent of the shift for the Fe(III)/Fe(II) couple , while the potential of the mixed-ligated diiron(III) porphyrin dimer is more positive compared to their monomeric analogue.”

“The spectral shift induced by imidazole correlated with inhibition of OsAOS1 activity, implying that imidazole may coordinate to ferric heme iron , triggering a heme-iron transition from high spin state to low spin state.”

“With the addition of axial ligand, the ferric ion of the dimers tends to bind with imidazole , and the intensity of the band 680 nm gradually decreases and disappears.”

“Addition of imidazole to a solution of the ferric variant results in the formation of a species axially coordinated by imidazole and histidine-63.”