Heme derivatives

Synthetic and structural chemistry of heme derivatives with nitrogen oxide ligands 99ACR350. 

Novel species developed for molecular switching have magnetic Fe304 particles linked to the control moiety by derivatized silicate linkages. Two of the control units themselves contain iron, in a ferrocene derivative and in a heme derivative. 

This enzyme [EC 1.11.1.5], having a heme derivative as a cofactor, catalyzes the reaction of two ferrocytochrome c with hydrogen peroxide to produce two ferricytochrome c and two water molecules. 

This model represents a natural starting point for both experimental and theoretical studies. Crystal structures have been reported for a number of heme derivatives with different substituents in the ring (22). FeTPP (TPP = meso-tetraphenylpor-phyrin) has been particularly widely used. Its electronic state is known experimentally to correspond to a low-spin triplet (S = 1). 

The symptoms of most porphyrias are now readily controlled with dietary changes or the administration of heme or heme derivatives. 

Although die role of iron in various heme derivatives and zinc in carboxypep-tidase and carbonic anhydrase is dear. Ihere are many instances in which little is known of the function of the trace metal. For example, it has been known for some time that ascidians ("sea squirts") concentrate vanadium from sea water by a factor of a millionfold, but a satisfactory explanation for its role in these animals remains elusive.117 There are many elements that are known to be usefol but for which no specific function has yet been proved. The list of known functions is expanding rapidly, however. 

Knowing that carbon monoxide complexes of hemes are dissociated by light, Warburg and Negelein, in 1928, determined the photochemical action spectrum (see Chapter 23) for reversal of the carbon monoxide inhibition of respiration of the yeast Torula utilis. The spectrum closely resembled the absorption spectrum of known heme derivatives (Fig. 16-7). Thus, it was proposed that 02, as well as CO, combines with the iron of the heme group in the Atmungsferment. 

Studies on silver(II) porphyrins have largely been centred on synthetic porphyrins, such as H2TPP and octaethylporphyrin, H2OEP. However, a range of complexes based on heme derivatives have also been described.552 Some of these latter complexes have been characterized by IR spectroscopy.553... 

Most of the numerous other riboflavin-containing enzymes contain FAD. FAD is an integral part of the biological oxidation-reduction system where it mediates the transfer of hydrogen ions from NAD11 to the oxidized cytochrome system. FAD can also accept hydrogen ions directly from a metabolite and transfer them to either NAD, a metal ion, a heme derivative, or molecular oxygen. The various mechanisms of action of FAD are probably due to differences in protein apoenzymes to which it is bound. 

Broumand, H., Ball, C.O., and Stier, E.F. 1958. Factors affecting the quality of prepackaged meat. II. E. Determining the proportions of heme derivatives in fresh meat. Food Technol. 12 65-77. 

Rosales-Hemandez MC, Correa-Basurto J, Flores-Sandoval C et al (2007) Theoretical study of heme derivatives under DFT calculations. Theochem 804 81-88... 

With the advent of Mossbauer spectroscopy, S7Fe-labeled heme derivatives have become increasingly important. However, the commercially available form of... 

These examples illustrate how MCD spectroscopy has been used to determine the identity of axial ligands in heme proteins through comparison of the MCD spectra of structurally defined systems with those of ill-defined heme derivatives. This approach has been successful in numerous cases involving studies of cytochrome P-450, chloroperoxi-dase, indoleamine 2,3-dioxygenase, secondary amine mono-oxygenase, hemoprotein H-450, and others (1,11-19). The remainder of this chapter addresses the issue of whether the approach just described that has... 

Despite the fact that the triclinic system is the only crystallographic system that unequivocally allows singlecrystal orientations to provide both enhanced in-plane and out-of-plane NRVS spectra, many other crystalline heme derivatives fortunately have all porphyrin planes close to being parallel to a common crystallographic plane. For example, [Fe(TPP)(l-MeIm)(NO)] has four independent porphyrin plane orientations, but all planes are within 13.8° of a common plane in the crystal. Data were collected using this common plane as the crystal-orienting plane to obtain an in-plane and an out-of-plane spectrum. As shown in Figure 10, a comparison of the in-plane , out-of-plane , and powder spectra show that useful intensity enhancements are still evident. Moreover, and fortunately, this situation of nearly coincident planes appears to be moderately frequently observed. 

Polymer-bound heme derivatives, physiological behavior of 88-YGK879. 

Figure 8.26. Representative Fe(II)/Fe(III) redox couples at pH = 7. (phen = phen-anthroline sal = salicylate porph = porphyrin = valid for [HCO = 10 M.) Complex formation with Fe(II) and Fe(III) both on solid and solute phases has a dramatic effect on the redox potentials thus electron transfer by the Fe(II),Fe(III) system can occur at pH = 7 over the entire range of the stability of water (-0.5 to 1.1 V). (= Fe 0)2 Fe refers to Fe adsorbed inner-spherically to a surface of a hydrous ferric oxide. The range of redox potentials for heme derivatives given on the right illustrates the possibilities involved in bioinorganic systems.

We report a few examples of enzyme inhibition using heme derivatives that either target enzymes acting on heme or enzymes that are affected by heme binding. 

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