Dántola M Laura, Neyra Recky Jael R, Lorente Carolina, Thomas Andrés H
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, La Plata, Argentina.
Photochem Photobiol. 2022 May;98(3):687-695. doi: 10.1111/php.13557. Epub 2021 Nov 17.
In electron-transfer initiated photosensitization processes, molecular oxygen (O ) is not involved in the first bimolecular event, but almost always participates in subsequent steps giving rise to oxygenated products. An exception to this general behavior is the photosensitized dimerization of tyrosine (Tyr), where O does not participate as a reactant in any step of the pathway yielding Tyr dimers (Tyr ). In the pterin (Ptr) photosensitized oxidation of Tyr, O does not directly participate in the formation of Tyr and quenches the triplet excited state of Ptr, the reactive species that initiates the process. However, O is necessary for the dimerization, phenomenon that we have named as the oxygen paradox. Here, we review the literature on the photosensitized formation of Tyr and present results of steady-state and time resolved experiments, in search of a mechanistic model to explain the contradictory role of O in this photochemical reaction system.
在电子转移引发的光敏化过程中，分子氧（O₂）不参与第一步双分子反应，但几乎总是参与后续步骤，从而产生氧化产物。这种一般行为的一个例外是酪氨酸（Tyr）的光敏二聚化，在生成酪氨酸二聚体（Tyr₂）的反应途径的任何步骤中，O₂都不作为反应物参与。在蝶呤（Ptr）光敏氧化酪氨酸的过程中，O₂不直接参与Tyr₂的形成，而是淬灭了Ptr的三重激发态，而Ptr的三重激发态是引发该过程的活性物种。然而，O₂对于二聚化是必需的，我们将这种现象称为氧悖论。在这里，我们综述了关于Tyr₂光敏形成的文献，并展示了稳态和时间分辨实验的结果，以寻找一个机理模型来解释O₂在这个光化学反应体系中的矛盾作用。
