Myoglobin, iron liganding

Ozaki SI, Roach MP, Matsui T, Watanabe Y (2001) Investigations of the roles of the distal heme environment and the proximal heme iron ligand in peroxide activation by heme enzymes via molecular engineering of myoglobin. Acc Chem Res 34 818-825... 

The IR spectra of the spin-transition complexes [Fe(L)3] , where L = IH-l,2,4-triazole and derivatives, showed characteristic shifts in vFeN modes between the high-spin and low-spin states. A resonance Raman band (180-250 cm" ) was ascribed to iron-ligand out-of-plane modes in mutant H93G myoglobin - its position is markedly dependent on the nature of the axial ligand. A normal-coordinate analysis shows that this band has vFe-L character, but also a significant contribution from iron-haem doming. ... 

FIGURE 15.25 The six liganding positions of an iron ion. Four ligands lie in the same plane the remaining two are, respectively, above and below this plane. In myoglobin. His F8 is the fifth ligand in oxymyoglobin, O9 becomes the sixth. 

That the environment could play a major role in determining ligand binding to iron in heme models and, probably, in myoglobin also, is in agreement with the conclusions of site-directed... 

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