The photodynamic effects of the cationic TMPyP (meso-tetrakis [N-methyl-4-pyridyl]porphyrin) and the anionic TPPS4 (meso-tetrakis[4-sulfonatophenyl]porphyrin) against PC/CL phosphatidylcholine/cardiolipin (85/15%) membranes were probed to address the influence of phorphyrin binding on lipid damage. Electronic absorption spectroscopy and zeta potential measurements demonstrated that only TMPyP binds to PC/CL large unilamellar vesicles (LUVs). The photodamage after irradiation with visible light was analyzed by dosages of lipid peroxides (LOOH) and thiobarbituric reactive substance and by a contrast phase image of the giant unilamellar vesicles (GUVs). Damage to LUVs and GUVs promoted by TMPyP and TPPS4 were qualitatively and quantitatively different. The cationic porphyrin promoted damage more extensive and faster. The increase in LOOH was higher in the presence of D2O, and was impaired by sodium azide and sorbic acid. The effect of D2O was higher for TPPS4 as the photosensitizer. The use of DCFH demonstrated that liposomes prevent the photobleaching of TMPyP. The results are consistent with a more stable TMPyP that generates long-lived singlet oxygen preferentially partitioned in the bilayer. Conversely, TPPS4 generates singlet oxygen in the bulk whose lifetime is increased in D2O. Therefore, the affinity of the porphyrin to the membrane modulates the rate, type and degree of lipid damage.

Fatores estruturais que modulam a atividade das porfirinas englobam os ligantes equatoriais, o metal central e o número e estrutura dos seus ligantes axiais. A esses fatores se associam o microambiente fornecido por apoproteínas, solventes e membranas. Porfirinas são bastante utilizadas para a construção de estruturas supramoleculares com diferentes aplicações. A modulação da atividade das porfirinas tem sido freqüentemente obtida pela imitação da natureza, ou seja, fornecimento de diferentes microambientes. A associação das porfirinas a nanoestruturas lipídicas pode mudar a atividade destes compostos de tal forma a mimetizar diferentes enzimas como a SOD, citocromo P450, peroxidases e outros. As formas reativas das porfirinas são estados de alta valência: metal-oxo-p cátion e metal-oxo produzidos pela reação com peróxidos e perácidos. A modulação da atividade de porfirinas por nanoestruturas lipídicas também tem sido obtida para hemeproteínas uma vez que nanoestruturas lipídicas afetam a conformação das proteínas. The structural factors modulating porphyrin activity encompass pyrrole and equatorial ligands, as well as the central metal and the number and structure of their axial ligands. Of equal importance is the microenvironment provided by apoproteins, solvents and membranes. Porphyrins are often used to construct supramolecular structures with different applications. The modulation of activity of the porphyrins has been frequently achieved by mimicking nature, i.e., by the provision of different microenvironments for these molecules. The association of porphyrins to surfactant-and lipid-containing nanostructures has changed the activity of these compounds to mimic different enzymes such as SOD, cytochrome P450, peroxidases and others. In determined conditions, the reactive forms of the porphyrins are high-valence states of oxo-metal-p cations and oxo-metal produced by the reaction with peroxides and peracids. The modulation of porphyrin activity by surfactant-and lipid-containing nanostructures has also been achieved for hemeproteins, as the lipid nanostructures affect the conformation of proteins.

C h emIn fo rm 2 0 1 2 , 4 3 , issu e 1 0 © 2 0 1 2 Wiley -VCH Verl ag G m b H & Co. K G a A , We i n he i m O r g an i c c h em i st r y Z 020 0 DOI: 1 0.100 2/ch in.201 2102 59 M o dulation of the C ataly t ic A ctivity of Porphyrins by L ipid-a nd Surfact a nt--Containing N anos tr uctur es -[8 2 ref s.]. -(NA N TES , I . L.; DU RA N, N . ; P IN TO, S . M . S . ; DA S IL VA, F . B. ; DE S O UZ A, J. S . ; IS OD A , N . ; L UZ , R . A . S . ; DE OLIVEIR A, T. G.; FE RNANDES, V. G.; J. Braz . Chem . Soc . 22 (201 1) 9, 1621 -1 633 ; C e nt. Cienc . Human as, Un iv. Fe d. AB C, 09 210-17 0 San to Andre, Braz il; Eng.) -Me i e r 10 -25 9

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