Castaño Carolina, Dántola María L, Oliveros Esther, Thomas Andrés H, Lorente Carolina
Departamento de Química, Facultad de Ciencias Exactas, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina.
Photochem Photobiol. 2013 Nov-Dec;89(6):1448-55. doi: 10.1111/php.12099. Epub 2013 Jun 27.
Pterins, heterocyclic compounds widespread in biological systems, accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. Pterins have been previously identified as good photosensitizers under UV-A irradiation. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of tyrosine (Tyr) in aqueous solutions. Tyr is an important target in the study of the photodynamic effects of UV-A radiation because it is oxidized by singlet oxygen ((1)O2) and plays a key role in polymerization and cross-linking of proteins. Steady UV-A irradiation of solutions containing Ptr and Tyr led to the consumption of Tyr and dissolved O2, whereas the Ptr concentration remained unchanged. Concomitantly, hydrogen peroxide (H2O2) was produced. By combining different analytical techniques, we could establish that the mechanism of the photosensitized process involves an electron transfer from Tyr to the triplet excited state of Ptr. Mass spectrometry, chromatography and fluorescence were used to analyze the photoproducts. In particular, oxygenated and dimeric compounds were identified.
蝶呤是广泛存在于生物系统中的杂环化合物，在患有白癜风（一种慢性色素脱失性疾病）的患者皮肤中会积累。蝶呤此前已被确定为在紫外线A照射下的良好光敏剂。在这项工作中，我们研究了氧化蝶呤的母体化合物蝶呤（Ptr）在水溶液中光敏化酪氨酸（Tyr）氧化的能力。Tyr是紫外线A辐射光动力效应研究中的一个重要靶点，因为它会被单线态氧（¹O₂）氧化，并且在蛋白质的聚合和交联中起关键作用。对含有Ptr和Tyr的溶液进行稳定的紫外线A照射会导致Tyr和溶解氧的消耗，而Ptr浓度保持不变。同时，会产生过氧化氢（H₂O₂）。通过结合不同的分析技术，我们可以确定光敏化过程的机制涉及电子从Tyr转移到Ptr的三重激发态。使用质谱、色谱和荧光分析光产物。特别地，鉴定出了氧化和二聚化合物。
