Iron mesoporphyrin

Figure 3. Structures of iron protoporphyrin IX (protoheme IX) (left) and iron mesoporphyrin IX (mesoheme IX) (right).

Mihara and co-workers (120, 123) have shown in a self-assembly system composed of a helix-disulfide-helix and an iron(III) mesoporphyrin... 

Peptide Ac-AKEAAHAEAAEAA-NH2 was synthesized using Boc chemistry on MBHA resin (100-200 mesh, 1% DVB, substitution level 0.53 mmol-g 1). Purification was carried out by HPLC on a 2.2-cm Vydac C18 column using a gradient of MeCN/H,0 in 0.1% TFA (5 to 40% over 40 min) at a flow rate of SmL-min Mesoporphyrin IX was converted into the iron(III) complex by refluxing with excess Fe(OAc)2 in AcOH.11"1 The bis(4-nitrophenyl) ester of iron(III) mesoporphyrin IX was subsequently prepared using the method of Collman et al.12001... 

An aliquot of Ac-AKEAAHAEAAEAA-NH, in H,0 was placed in a preweighed 1.5-mL microcentrifuge tube and lyophilized to dryness. The dried powder (15 mg, 11.7 pmol) was dissolved in dry DMSO (100 pL) and 29 pM bis(p-nitrophenyl) ester of iron(III) mesoporphyrin IX in DMSO (100 pL) was added, followed by DIPEA (45 pL, 22 equiv). The soln was warmed to 40 °C until HPLC indicated no further reaction (ca. 3h). It was then diluted to 1.0 mL with 50 mM NaOAc, pH 6, and purified by sequential ion-exchange chromatography (Sephadex CM50 50 mM NaOAc, pH 6), RP-HPLC (Vydac... 

Kurland et al. (64) observed hyperfine-shifted resonances of ferrimyoglobin between —20 and —90 ppm. Comparison with the spectra of the iron(III)-complexes with protoporphyrin IX, deuteroporphyrin IX, and mesoporphyrin IX seems to indicate that four of the low field resonances correspond to the four ring methyl groups. Additional lines at high fields from DSS were observed in ferrimyoglobin (116), and in high spin porphyrin-iron(III) complexes (Caughey et al. (19)). The observation... 

In a recent discussion of the spectra of haem-compounds, one of us (10) suggested that d—d transitions, as well as charge transfer bands, could be responsible for part of the near infra-red absorption, and that n—ji triplets could also be involved. In particular this could be the case for the weaker bands in the mesoporphyrin iron methoxide spectrum. The strongest band in the near infra-red, which is the only one seen clearly in haemoproteins, is very probably largely charge transfer. The... 

The simple haem mesoporphyrin IX iron(III) methoxide has a relatively weak near infra-red band at 13.1 kK (101). The region 8—10 kK can then be studied in more detail. This compound is essentially high-spin (8, 87, 101) and the crystal structure is known in detail (8). The polarized crystal spectrum in the region 5—12 kK has been measured (96) and all the bands are in-plane polarized. Peaks are seen at 11.4, 9.3, 8.3 and 7.2 kK, with a shoulder at 10.2 kK. The bands are so evenly spaced as to suggest a vibrational progression, and the interval of about 1.1 kK is about the same as the usually a—/J separation in typical metalloporphy-rin spectra. This absorption could be due to the low-spin form the extinction coefficients are around 50, and protoporphyrin IX iron(III) methoxide, which has a very similar visible spectrum (101), has a magnetic moment (8) which suggests the presence of some 20% of the low-spin form. 

FECH (also known as heme synthase) is an iron-sulfur protein located in the inner mitochondrial membrane. This enzyme inserts ferrous iron into protoporphyrin to form heme During this process, two hydrogens are displaced from the ring nitrogens. Other metals in the divalent state will also act as substrate, yielding the corresponding chelate (e.g., incorporation of Zn into protoporphyrin to yield zinc protoporphyrin). In iron-deficient states Zn successfully competes with Fe in developing red cells so that the concentration of zinc protoporphyrin in erythrocytes increases. Furthermore, other dicarboxylic porphyrins will also serve as substrates (e.g., mesoporphyrin). 

Manganese(VI) complexes, 109-111 Manganese(VII) complexes, 109-111 Marcasite, 1240 Mercury compounds ruthenium complexes, 280 Mesoperrhenates, 198 Mesoporphyrin iron complexes, 1266 Methemerythrin, 254 Molybdenum-iron-sulfur complexes, 241 MOssbauer spectroscopy iron, 1181... 

Clezy s modification of the MacDonald synthesis using a 5,5 -diformyl-pyrro-ketone instead of a diformyl-pyrromethane has been extended to the synthesis of the a-oxy-derivative of mesoporphyrin IX and to the y-oxy-derivative of protoporphyrin IX (Scheme 3). The iron complex of the latter undergoes oxidative ring opening in pyridine solution to form biliverdin IX-y (25), the parent compound of a series of three green pigments found in certain types of butterflies and caterpillars this provides a model for their probable mode of biosynthesis. 

Axial base chelation was similarly used to prepare a symmetric diheme Meso-1,2-di-(3-pyridyl)ethylenediamine (31) was coupled with mesoporphyrin monomethyl ester 32 through the pivaloyl anhydride, followed by iron insertion to give the diheme 33 (Scheme 16). The reaction with CO exhibits two rate constants, indicating either two environments or a sequential change of environment due to cooperativity. 

Day et al. (1967a) have obtained the crystal spectra (range 16,000 to 5000 cm ) of mesoporphyrin IX iron (III) methoxide, ten myoglobin derivatives, and cytochrome c peroxidase. The comparison between these spectra and the corresponding solution spectra show that in all cases there is a reduction in intensity of absorption bands in the solid state, but that in most cases the energy of the spectrum is virtually unchanged. Myoglobin fluoride and cytochrome c peroxidase are exceptions. 

The polarization of all the bands in the heme spectra from 25,000 to 5000 cm " is in-plane. The proposed character of the transitions at 20,000, 16,000, and 10,000 cm as being mixed charge-transfer and ligand bands (Day et al., 1964) was supported by the polarization data of Day et al. (1967a), for the symmetry of all the transitions was of necessity the same and, as the transitions of the ligand were in-plane, was required to be in-plane. Besides these bands there is a series of very weak bands at 7200,8300, and 9400 cm Mn the spectra of the mesoporphyrin IX iron (III) methoxide crystals. These are possibly spin-forbidden components of the lowest electronic excited state, all polarized in the same direction, i.e., in the heme plane. Sharp, weak bands at lower wave numbers were assigned to vibrational overtones. 

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