Iron porphyrin models

Simonneaux G, Le Maux P (2006) Carbene Complexes of Heme Proteins and Iron Porphyrin Models. 17 83-122... 

III. Iron-Porphyrin Model Compounds A. Fe(III) Hemin Compounds... 

G. Simonneaux and A. Bondon, Isocyanides and Phosphines as Axial Ligands in Heme Proteins and Iron Porphyrin Models, in The Porphyrin Handbook , eds. K. M. Kadish, K. M. Smith, and R. Guilard, Academic Press, New York, 2000, Vol. 5,p. 300. 

Line shape analysis has been utilized to detect and elucidate dynamics of ligands bound to metals. For iron porphyrin models of metalloproteins, axial imidazole ligands may rotate relative to the heme axes linebroadening of heme substituents resulting from this process can be observed at low temperature. Such ligand motion is not commonly observed within metalloproteins because of constraints of the protein structure and metal-ligand bonding. NMR studies of... 

To model the binuclear center shown in Figure 6, 2ill histidines cire replaced by imidazoles, the tyrosine is replaced by a phenol and the heme group is replaced by an imsubstituted iron porphyrin. Models of this size can be used in calculations on certain intermediates, where the copper emd... 

Since the discovery of cytochrome P450 hemes, many questions have been resolved using iron porphyrin model systems. The first question concerns the nature of the iron complexes involved as intermediates in the catalytic cycle of dioxygen activation and substrate hydroxylation or epoxidation. The understanding of the mechanisms by which cytochrome P450 hemes act during the... 

It was later discovered that the reactive intermediates in the iron porphyrin model systems were high-valent oxoiron porphyrin complexes. A green oxoiron(IV) porphyrin cation radical species (13) has been well characterized by various spectroscopic techniques, including visible spectroscopy, NMR, EPR, Mossbauer, and EXAFS (Figure 1.11) . It has recently been shown by Nam and Que that the oxygen-atom transfer from certain iodosylarenes is reversible with some iron porphyrins. For the case of 1,2-difluoro-4-iodobenzene both an oxoferryl species and an iodosyl-ferric species were observed to be in equilibrium . 

Figure 6.52. Possible pathways for the oxidative decarboxylation of some therapeutic carboxylic acids catalyzed by both P450s and some iron-porphyrin model systems.

The iron porphyrin models discussed above all share a nearly planar porphine core, similar to the hone in Mb, whereas the heme in Cyt c is distorted from the planar structure by the covalent bonds and hydrogen bonds with surrounding protein residues. To address the effect of environmentally induced heme distortion on the mechanism of VER, rather than including the surrounding protein residues explicitly (too expensive for any reasonable high level of theory), we replaced the heme s central iron atom by nickel. Due to the smaller size of nickel relative to iron, the porphine structure is distorted in the Ni-substituted Ni-hane in a manner similar to the heme distortion observed in cytochrome c. Another nickel porphyrin model, nickel octa-ethylporphyrin (NiOEP), was also optimized to a structure with similar nonplanar porphine core geometry [90]. 

Zhang, Y Fujisaki, H. Straub, J. E., Direct evidence for mode-specific vibrational energy relaxation from quantum time-dependent perturbation theory. 1. Eive-coordinate ferrous iron porphyrin model. J. Chem. Phy. 2009, 130, 025102. 

Isocyanides and Phosphines as Axial Ligands in Heme Proteins and Iron Porphyrin Models Gerard Simonneaux... 

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