Porphyrins iron-containing

Iron-containing proteias are classified as either heme proteias or nonheme iron proteias. The former contain iron that is coordinated to a porphyrin... 

More recently 233) it has been reported that cross-linked polystyrene containing imidazole ligands did not provide a support rigid enough to prevent dimerization, and that the p-oxo dimer was benzene extracted from oxygenated tetraphenyl porphyrin iron(ll), Fe(TPP), which had been attached to the modified polystyrene. A discussion of model synthetic porphyrins, from which definitive structural and other physical data are obtained, is given in section V.C. 

Originally, this temperature variation of AEq was attributed to the dynamic distribution of the terminal oxygen of the Fe02-moiety, as suggested by X-ray structural results for picket-fence porphyrins [26,27]. This view is now supported by NFS studies which provide more information on dynamic processes in iron-containing molecules. 

Fig. 3. Schematic illustration of the iron linked groups in hemoproteins. The porphyrin ring containing the four pyrrole nitrogen atoms is shown as an elipsoid. The iron atom is 0.5 A out of the prophyrin plane in the direction of X (54). The axial ligands confirmed by crystallography (55, 56) are ...

In the case of iron-containing small molecule analogs of Mb and Hb a much rockier road to successful model compounds was encountered. Even though the syntheses of iron porphyrin complexes were carried out in analogous manner to the cobalt species described above, their irreversible oxidation to the p-oxo dimer upon... 

INTRODUCTION IRON-CONTAINING PROTEINS WITH PORPHYRIN LIGAND SYSTEMS... 

The preceding sections of Chapter 7 have discussed iron-containing proteins and enzymes having a porphyrin ring system. Section 7.9 presents a short introduction to the many non-heme iron-containing proteins and enzymes. Two of these are iron-sulfur proteins (Section 7.9.2) and iron-oxo proteins (Section 7.9.3). 

Porphyrin rings containing iron are also a feature of the cytochromes. Several cytochromes are responsible for the latter part of the electron transport chain of oxidative phosphorylation that provides the principal source of ATP for an aerobic cell (see Section 15.1.2). Their function involves alternate oxidation-reduction of the iron between Fe + (reduced form) and Fe + (oxidized form). The individual cytochromes vary structurally, and their classification (a, b, c, etc.) is related to their absorption maxima in the visible spectrum. They contain a haem system that is covalently bound to protein through thiol groups. 

Where the valency of a metal is not indicated, the normal valency of the metal is assumed. Beryllium probably is placed in the 0=N group because of the stability of its phthalocyanine chelate. Most often Be forms very stable bonds with oxygen as the donor element. Vanadium, nickel, and copper from the N > O group and iron from the ON group are the elements most frequently found in petroleum, chelated with porphyrin ligands. The porphyrin chelate contains four nitrogens as donor elements. 

The most important porphyrin derivatives are characterized by a central metal atom hemin is the iron-containing porphyrin essential to mammalian blood, and chlorophyll is the magnesium-containing porphyrin that catalyzes photosynthesis. Other derivatives include rhe cytochromes, which function in cellular metabolism, and the phthalocyanme group of dyes, Porphyrins are described in considerable detail m a 20-volume set of books, The Porphyrin Handbook, Academic Press, New York, NY, 2003. 

---