Hemin ester

The purity of the hemin ester can be checked by tic (silica gel, with CHC13/ methanol = 5 1), or by visible spectroscopy. A small amount of the hemin ester dissolved in pyridine can be reduced by sodium dithionite in a cuvette.1 2 The resultant hemochrome should exhibit two absorption maxima at 557 and 526 nm. If necessary, the product can be further purified by chromatography on an alumina (grade III) column (1X10 cm) using a mixture of chloroform and methanol (10 1) as eluent. However, the iron prophyrin compound obtained after chromatography exists as the p-oxo dimer, [Fe(III)-O-Fe(III)], which may be converted back to the chloride by treatment in CHC13 with dry HO followed by crystallization from chloroform/methanol. 

Dimethyl ester ferrichloride, CMHj Cl4FeN40 (green hemin ester), pleochroitic elongated platelets, no definite mp. Ferric chloride and HCl can be removed by washing the chloroform soln with water. 

Heme proteins, 262 electron transport, 263 Hemerythrin, 253 Hemin ester, 1266 Hemoglobin, 262,1257,1269 artificial, 100... 

When hemin (1) is treated with gaseous hydrogen chloride in anhydrous methanol/pyridine in the presence of iron(II) sulfate, protoporphyrin dimethyl ester (2), the metal-free ligand of hemin. is produced in almost quantitative yield. This compound is quite sensitive to oxygen... 

Other important porphyrins which can be derived from hemin are hematoporphyrin (5) and mesoporphyrin (6). Hematoporphyrin (5) which is commercially available at a relatively low price is sensitive towards acid due to the 1-hydroxyethyl groups, so commercial samples contain only 60 to 70% of hematoporphyrin. Pure hematoporphyrin dimethyl ester which is a racemic and diastereomeric mixture of four stereoisomers can be obtained by esterification with diazomethane and subsequent chromatography on neutral alumina.84 The pure stereoisomers can be prepared by enantioselective reduction of diacetyldeuteroporphyrin dimethyl ester.85a b The... 

A procedure for determination of lipid hydroperoxides in human plasma is based on kinetic measurement of the CL of luminol (124) with hemin (75a) catalysis . CLD of microperoxidase-catalyzed oxidation of luminol (124) or isoluminol (190) was applied to detection and determination of amino acid hydroperoxides after exposure to UV and y-irradiation A method for determination of hydroperoxides in the phospholipids of cultured cells uses isoluminol (190) and microperoxidase as catalyst " . Simultaneous determination of phosphatidylcholine hydroperoxides and cholesteryl ester hydroperoxides in human serum is carried out by quantitative extraction of the lipids, HPLC separation by column switching and CLD using isoluminol (190) with microperoxidase catalysis . ... 

Taking protoporphyrin-IX (19) as the inexpensive commercially available starting material for porphyrin manipulations, the common substituent reactions are shown in Scheme 8. Protoporphyrin-IX is usually obtained simply by demetallation of hemin, the most efficient route (which provides the dimethyl ester, ready for chromatographic purification) involving treatment with iron(II) sulfate in methanol containing HC1 gas. 

Figure 8. Docking interaction of hemin with artemisinin analogue 99 in Sybyl showing hydrogen bonding between hemin side chains and the C-3 ester group of analogue 99.

Another example, which demonstrates the modulation of the peroxidase activity of Mb by modification of the heme-propionate side chains, has been proposed by Casella and co-workers (75). They prepared a Mb reconstituted with peptide-linked hemin such as protohemin-L-arginyl-L-alanine or protohe-min-L-histidine methyl ester as shown in Fig. 20. The peroxidase activity toward small substrate oxidations by the reconstituted Mb slightly increased the fccat... 

Initial advances have been made in MCM synthesis and further studies are in progress [82]. It was not until recently that polymerization kinetics of such systems and properties of the resulting PCMU have received attention. Thus, radical polymerization of the dimethyl ester of hemin was carried out in 1977 [85]. The possibility of polymerizing 4-vinylpyridine (4-VP) complex-bound to Ru(II) (cis-[Ru(Dipy)2(4-VP)X]n+ complexes, where n = 1, X = Cl n = 2, X = CO or 4-VP) has been shown [86a] but the properties of the polymers obtained have... 

Materials. The TPPFeCl was prepared and purified by literature methods (16, 17). Octaethyl porphyrin was a gift from H. H. Inhoffen, and the hemin dimethyl ester [PP(IX)DMEFemCl] was purcased from Sigma Chemical Co. 

Dimethyl ester, C35HjSN,1Oi, green crystals from chloroform + petr ether. When produced from bilirubin, mp 215-223" synthetic 206-209" (rom hemin 208 from hemoglobin 216. ... 

The NMR spectra, which diflFer markedly from spectra for low- and high-spin iron (III) and low-spin iron (II) porphyrins in chemical shifts and in line widths, and infrared bands between 800 and 900 cm" have been particularly useful in estabhshing that FeOFe compounds can in fact be prepared from hemin A derivatives. For example, the diethyl ester, monoethyl ether derivative of heme A (Figure 15) when reduced... 

Figure 17. Proton magnetic resonance spectrum at 100 MHz of the fx-oxo dimer of hemin A monoethyl ether, diethyl ester in CDCls...

More recently, Molokoedov et al. have used protohemin monobenzyl ester 13, (obtained from protohemin dibenzyl ester 12 in 61% yield by partial hydrolysis), to prepare a series of histidine-containing peptide derivatives 14a- . Coupling of peptide and hemin was completed by the mixed anhydride method using ethyl chloroformate and triethylamine. The yields of product decreased from 47% to 25% as the length of the peptide chain increased, the products being obtained as a mixture of the 6- and 7-isomers... 

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