Protoporphyrin properties

Protoporphyrin-IX, N-methyl-, 4, 396 Protoporphyrins, 4, 382 photooxygenation, 4, 402 Prototropic tautomerism polyheteroatom six-membered rings, 3, 1055 Prozapine properties, 7, 545 Pschorr reaction carbolines from, 4, 523 dibenzazepines from, 7, 533 dibenzothiophenes from, 4, 107 phenanthridines from, 2, 433 Pseudilin, pentabromo-synthesis, 1, 449 Pseudoazulene synthesis, 4, 526 Pseudobases in synthesis reviews, 1, 62 Pseudocyanines, 2, 331 Pseudothiohydantoin synthesis, 6, 296 Pseudouracil structure, 3, 68 Pseudoyangonin IR spectra, 3, 596 Pseudoyohimbine synthesis, 2, 271 Psicofuranine biological activity, 5, 603 as pharmaceutical, 1, 153, 160... 

The second methodology involves direct introduction of glycosylated moieties onto a suitably functionalized meso-arylporphyrin scaffold, accessible from a natural source (protoporphyrin-IX) or by total synthesis. Several O-,133,145,146 S-,147 and N-glycoporphyrins148 (125-129) have thus been prepared (Fig. 12). Moreover, in order to explore the influence of the clustered peripheral saccharides around the porphyrin scaffolds, and to evaluate their photophysical properties, the synthesis of dodecavalent porphyrins bearing four trivalent glycodendrons via amide ligation (129) has been achieved.149... 

Ohlstein, E. H., Wood, K. S., and Ignarro, L. J. (1982). Purification and properties of heme-deficient hepatic soluble guanylate cyclase Effects of heme and other factors on enzyme activation by NO, NO-heme, and protoporphyrin IX. Arch. Biochem. Biophys. 218, 187-198. 

Some of the key properties of a photosensitizer are high efficiency of singlet-oxygen generation, strong absorption in the red and particularly near-IR (660-800 nm), preferential affinity for tumor rather than healthy tissue, and rapid clearance from the body. Porphyrin and phthalocyanine dyes fit these criteria best, and much work has been done on these dye types [76], Photofrin, a hemato-porphyrin derivative, was the first photosensitizer to be approved for clinical use. It is a complex mixture of monomeric porphyrins (protoporphyrin, hematopor-phyrin (84), and hydroxyethylvinyldeuteroporphyrin) and oligomers of these porphyrins. 

One of the variables in the structures of the porphyrins present in heme proteins is the presence or absence of vinyl substituents on the periphery of the macrocycle. For example, b hemes have vinyl substituents whereas c hemes do not. Because of the sensitivity of such vinyl substituents during synthetic transformations, it has often been desirable to use octa-alkyl porphyrins in model studies of the spectroscopic properties of heme systems. The development of improved methods for the preparation of octa-alkyl porphyrins has likewise increased the availability of such porphyrins for model studies (20, 21). To assess the effect that replacement of the two vinyl substituents in protoporphyrin IX with alkyl (ethyl) groups has on the MCD properties of the heme system, an extensive and systematic study of the MCD properties of mesoheme IX-reconstituted myoglobin and horseradish peroxidase in comparison with the spectra of the native protoheme-bound proteins has been carried out (22). The structures of these two porphyrins are shown in Figure 3. 

The construction and properties of monolayers has been well documented by Kuhn (1979) and the photochemical reactions which occur in such systems reviewed (Whitten et al., 1977). Molecules in monolayers are usually ordered and in the case of rru/i -azastilbenes irradiation of the ordered array produces excimer emission and dimers (Whitten, 1979 Quina et al, 1976 Quina and Whitten, 1977). This contrasts with what is found when the fra/jj-isomers of such compounds are incorporated into micelles. In such systems the predominant reaction is cis-trans isomerisation excimer emission is lacking. It is suggested that the lack of isomerisation in the fatty acid monolayers is due to the tight packing and consequent high viscosity of such systems. Styrene also dimerises in a fatty acid monolayer. Interestingly, the products formed on photo-oxidation of protoporphyrins are dependent upon whether the reaction is carried out in a monolayer or a micelle (Whitten et al., 1978). Zinc octa-ethylporphyrin exhibits excimer emission in monolayers (Zachariasse and Whitten, 1973). Porphyrins are photoreduced by amines in monolayers (Mercer-Smith and Whitten, 1979). Electron-transfer reactions have been carried out with monolayers of stearic acid containing chlorophyll and electron acceptors such as quinones (Janzen et al., 1979 Janzen and Bolton, 1979). 

All the remaining questions focus on comparisons of CCP, MMB, and CAT. The first question addressed is Can the differences in the active site of CCP, MMB, and CAT account for the differences in their observed electromagnetic properties MMB and CCP (55, 56) have been found to have the same heme unit, a ferric protoporphyrin-IX with a water and an imidazole as axial ligands. CAT has a single... 

This section firstly includes discussion of the NMR properties of certain paramagnetic porphyrins and is then concerned with recent developments in the study of the heme proteins cytochrome c and myoglobin, both of which comprise single polypeptide chains to which a protoporphyrin IX is bound, and hemoglobin which consists of four subunit heme polypeptides. 

This esterified hemin is soluble in ligating solvents such as pyridine and also halogenated hydrocarbons, ethers such as tetrahydrofuran, and benzene. It is slightly soluble in alcohols and insoluble in water. In the presence of traces of water in a solution it will slowly convert to the n-oxo form. It can also dehydrate to the proto forms i under specific conditions. Other chemical, physical, and biological properties are similar to those for the protoporphyrin IX com-plex.i Extinction coefficients for the various characteristic spectra of this material are not well defined, as the solutions are generally unstable with time, going to mixtures of the various ligated and jx-oxo forms. 

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