Foto-oxidação de proteínas por porfirinas hidrossolúveis
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Data
2024-01-29
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Universidade Federal de Goiás
Resumo
Photodynamic Therapy (PDT) is a growing therapy, indicated as an alternative to the treatment of microorganisms and various types of cancer. For its operation, three components are necessary: molecular oxygen, visible light and a photosensitizer (FS). Among the most used FS are porphyrins, which can be cationic or anionic depending on the peripheral charge of their structure. In systemic administration, FS travel through the bloodstream, making it possible to interact with body elements such as proteins, which can be photo-oxidized with controlled administration of light, losing their function, whether structurally or functionally, which can cause death. cell of target tissues. The present work analyzed the photo-oxidation of bovine serum albumin (BSA) by two cationic (TMPyP and ZnTMPyP) and two anionic (TPPS and ZnTPPS) water-soluble porphyrins. The effect of the presence of the metallic atom in the central ring of the porphyrin was analyzed; two types of irradiation sources (a halogen source and a laser module emitting at 532 mn); the effect of BSA on the production of singlet oxygen and, finally, the effect of adding constant photo-oxidation oxygen. Initially, a protocol was found that allowed the reproductive obtainment of photo-oxidation constants. Subsequently, it was observed that the photo-oxidation constant is greater for cationic porphyrins, due to their greater proximity to the fluorescent residue tryptophan, and increases with the presence of zinc, which, as it is a heavy atom, favors the process of intersystem crossing and production. of reactive species. It was also observed that the halogen lamp provides faster degradation than the laser, which may be associated with its greater spectral amplitude and could oxidize other albumin components. Furthermore, it was possible to conclude that BSA acts as an obstacle between FS and molecular oxygen, reducing the formation of singlet oxygen, which made it necessary to add oxygen gas to the solution to obtain a phosphorescence signal, which promotes a reduction in photo-oxidative rate. Our hypothesis is that rapid photo-oxidation at the beginning of the process can change the conformation of BSA, blocking oxygen access. The results obtained here are valuable for the study of protein photo-oxidation and can be extended to other biological structures targeted for studies on photodynamic action.
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Palavras-chave
Fotodegradação, Porfirinas, Triptofano, PDT, Photodegradation, Porphyrins, Tryptophan
Citação
ARANTES, Ariane Gornates. Foto-oxidação de proteínas por porfirinas hidrossolúveis. 2024. 51 f. Trabalho de Conclusão de Curso (Bacharelado em Física Médica) - Instituto de Física, Universidade Federal de Goiás, Goiânia, 2024.