Martínez Ana, López-Rull Isabel, Fargallo Juan A
Departamento de Materiales de Baja Dimensionalidad, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior S. N., Ciudad Universitaria, Ciudad de México 04510, Mexico.
Departamento Biología y Geología, Física y Química Inorgánica, Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, C/Tulipán s/n., 28933 Madrid, Spain.
Antioxidants (Basel). 2023 Aug 23;12(9):1662. doi: 10.3390/antiox12091662.
The pigments responsible for eggshell color and patterning in birds are protoporphyrin IX (PP) and biliverdin (BV). Both are involved in the catalytic degradation of the hemo group. Bilirubin (BR), another pigment, is produced when BV is broken down. PP, BV, and BR are free radical scavengers. In this study, we theoretically investigated the antioxidant capacities of these three biological meaningful molecules using Density Functional Theory calculations. First, two antioxidant mechanisms were analyzed for PP, BV, and BR: electron transfer and Hydrogen Atom Transfer. Second, since PP and BV interact with the calcium carbonate matrix of the eggshell, we analyzed the interaction of these pigments with Ca and investigated their chelate compounds. Third, we explored the pro-oxidant properties of PP and BV, which have been proposed for PP when photoactivated to the triplet state, but not for BV. Our results show that PP, BV, and BR are just as good antiradical as other important natural pigments (carotenoids). Neither the antiradical properties of PP and BV nor the UV-visible spectra change due to the presence of calcium, suggesting that the signaling function of these pigments is not affected by the link with Ca. Finally, we found that both PP and BV (alone and when linked to Ca) can transfer energy from its triplet state to molecular-oxygen-producing singlet oxygen, indicating their pro-oxidant capacity. This investigation answers important questions about the function of these pigments, which may help to understand their influence on the reproductive success of birds.
鸟类蛋壳颜色和图案形成所涉及的色素是原卟啉IX（PP）和胆绿素（BV）。二者均参与血红素基团的催化降解。另一种色素胆红素（BR）是在BV分解时产生的。PP、BV和BR都是自由基清除剂。在本研究中，我们使用密度泛函理论计算从理论上研究了这三种具有生物学意义的分子的抗氧化能力。首先，分析了PP、BV和BR的两种抗氧化机制：电子转移和氢原子转移。其次，由于PP和BV与蛋壳的碳酸钙基质相互作用，我们分析了这些色素与钙的相互作用，并研究了它们的螯合物。第三，我们探究了PP和BV的促氧化特性，有人提出PP在光激发到三重态时具有促氧化特性，但BV没有。我们的结果表明，PP、BV和BR与其他重要的天然色素（类胡萝卜素）一样，具有良好的抗自由基能力。PP和BV的抗自由基特性以及紫外可见光谱都不会因钙的存在而改变，这表明这些色素的信号功能不受与钙结合的影响。最后，我们发现PP和BV（单独存在以及与钙结合时）都可以将其三重态的能量转移给产分子氧的单线态氧，表明它们具有促氧化能力。这项研究回答了有关这些色素功能的重要问题，这可能有助于理解它们对鸟类繁殖成功的影响。
