Hemes, polymer-bound

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

TEAA, K3Fe(CN)6 and non-heme iron catalysts.Polymer-bound 0s04, and encapsulated OSO4 have been shown to give the diol in the presence of as well as OSO4 on an ion exchange resin. DUiydroxylation has... 

Table 1. Oxygen- and carbon monoxide-binding rate constants and affinities for the polymer-bound hemes in aqueous media...

Because coordinatively bound complexes are quite easy to prepare, numerous papers on this subject have been published. Soluble complexes are prepared by dissolving stoichiometric amounts of polymer and metal complex in an organic solvent or water. To obtain solid materials, the solvent is removed or a film is cast. Cross-linked insoluble polymers are suspended in a solvent and a solution of a metal complex is added. The equilibrium of the coordinatively polymer-bound metal complex with the unbound one in solution is not favorable (Eq. 5-6), so an excess of strong low molecular weight donor base can destroy the polymer coordinative bond. Even the heme in myoglobin can be cleaved to give the apomyoglobin, as described in Section 2.3.1, and another porphyrin derivative subsequently coordinatively bound. 

We have studied the oxygenation of ferroheme bound to a polymer ligand in the solid state98. The profiles of oxygen uptake by powders of polymer-heme complexes were measured by volumetry, as shown in Fig. 22. The heme complex embedded in the porous polymer matrix or in the poly(electrolyte) aggregate takes up... 

Myoglobin and a cytochrome bound to gold electrodes are electroactive. A second monolayer shows a third of the electroactivity of the first a third monolayer is redox-inactive. Inert separating polymers such as poly(styrenesul-fonate) or poly(dimethyl diallyl) anunonium chloride do not substantially inhibit electron transfer if the heme protein is separated by less than 4 nm (Lvov etal, 1998). 

Hemosiderin, a mammalian non-heme iron storage protein with a similar function to ferritin. It contains iron oxyhy-droxide cores similar to those of ferritin, and it has been reported that these cores are present as large, dense, membrane-bound aggregates in vivo. It is assumed that hemosiderin is produced by lysosomal degradation of ferritin or possibly of ferritin polymers. Hemosiderin is deposited in the liver and spleen, especially in diseases such as pernicious anemia or hemochromatosis. The deposits are yellow to brown-red pigments. The iron content of hemosiderin is about 37%. Nonheme iron is also abundantly present in the brain in different forms. In the so-called high-molecular-weight complexes, iron is bound to hemosiderin and ferritin. The total amount of iron may differ in health and disease [F. A. Fischbach et al, J. Ultrastruct. Res. 1971, 37, 495 M. P. Weir, T. J. Peters, Biochem.J. 1984, 223, 31]. 

In the example of Figure 20, the heme of cytochrome 562 of Escherichia coli is bound within a protein bundle by coordination of the heme s iron to a methionine and a histidine." Attachment of a modified heme (iron porphyrin derivative) to the protein s surface is performed via mutation of the histidine 63 to introduce a cysteine residue opposite to the heme pocket. The subsequent removal of the native heme leaves a protein receptor that can self-assemble by ligation of the pendant external heme in a neighboring heme pocket. The assemblies have some flexibility, as shown by the bends observed in AFM images of the polymers. The right amount of flexibility was important in obtaining a 100-mer that was approximately 350 nm long. 

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