Metalloporphyrins Interaction with

Porphyrin and Metalloporphyrin Interactions with Nucleic Acids Robert F. Pasternack and Esther J. Gibbs... 

In related work, Martiney et al. showed that metalloporphyrins with zinc or tin were capable of inhibiting hemozoin formation in trophozoite extracts [105]. Zn(II) and Sn(IV) analogs of heme were selected for study as a result of their known competitive interactions with heme in a number of systems and their use as pharmacological photosensitizers. The order of efficacy for these metalloporphyrins was ZnDPIX>SnPPIX ZnPPIX. This order is consistent with the proposed... 

Intestinal absorption studies of Mn-MP were undertaken in an effort to assess the viability of the metalloporphyrin as an oral hepatobiliary agent [101, 102]. Mixed micelles of Mn-MP complexed with monoolein and taurocholate were administered to rats, resulting in liver image enhancement 68% above baseline levels six hours after administration [101]. In pigs, the mixed micelle preparation showed variable enhancement over 24 hours. Observation that Mn-MP interacts with oleic acid vesicles [103] led to investigations of the effect of oleic acid on the absorption rate of Mn-MP from the small bowel into the circulatory system [102,104]. The increase in absorption of the complex was mediated by a decrease in the relaxivity of the metalloporphyrin resulting from the interaction with the lipid vesicles. 

The last decade has greatly increased our knowledge on how metallo-porphyrins are able to interact with hydrogen peroxide without producing the unspecific hydroxyl radical. It would therefore appear likely that in the near future, industrial applications of such metalloporphyrins with hydrogen peroxide will be started in earnest. 

It has been found that in two component systems zinc (II) porphyrin-ligand coordination properties of the metalloporphyrins increase in the following order ZnTPhPelectron effects of peripheral substitutes. In three component systems zinc (II) porphyrin-ligand-benzene the mentioned above properties change in the following order ZnPP>ZnDP>ZnHP>ZnTPhP and are inversely proportional to an ability of the macrocycle to 7r-7i-interactions with benzene. Thus, the new approach to molecular recognition based on specific salvation 71-71-interactions is demonstrated on example of znc (II) porphyrins. 

In such porphine compounds, the Mg atom. is CormaIIy-4-coorinteraction with either water or other solvent molecules is a common, if not universal, occurrence further, in chlorophyll, interaction with the keto group at position 9 in another molecule is also established. It also appears that 5-coordination is preferred over 6-coordination as in the structure of magnesium tetraphenylporphyrin hydrate,30 where the Mg atom is out of the plane of the N atoms and is approximately square pyramidal. Although Mg and other metalloporphyrins can undergo oxidation31 by one-electron changes, for Mg it is the macrocycle and not the metal that is involved. 

The pairing of anion radicals with their counter cations is a wide-spread and now well documented phenomenon (Szwarc, 1972). In contrast, ion-pair phenomena in cation radical systems are not common, but see p. 222. Shifts in -values caused by halide-ion interaction with the tetramethoxybenzene cation radical have been reported (Sullivan, 1973), and halide-ion splittings of metalloporphyrin cation radical esr spectra have been demonstrated (Fajer et al., 1973). 

Fuhrhop, J.-H., Lehmann, T. (1984). Metalloporphyrins in polymeric matrices, micelles and vesicles VI hydrophobic and hydrophilic derivatives of 3,8-di-formyldeutero-porphyrin-dimethylester and their interaction with vesicles, Liebigs Ann. Chem., p. 1057. 

The observation that light accelerates these reactions can be rationalized in the framework of the above interpretation. Since light passed through a solution of vanadyl etioporphyrin I without effect on the system, it would appear that photochemically excited species of metalloporphyrins are responsible for the faster reactions as a consequence of their enhanced capability of interaction with halogens and the other reagents. 

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