Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil.
Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, 31270-901, Brazil.
Free Radic Biol Med. 2022 Feb 20;180:143-152. doi: 10.1016/j.freeradbiomed.2021.12.303. Epub 2022 Jan 1.
The use of spin traps and redox probes coupled with electron paramagnetic resonance (EPR) is a method frequently applied in the evaluation of the efficiency of photosensitizers and photocatalysts in phototherapeutic and photocatalytic processes that involve reactive oxygen species. In this way, the method helps to clarify the mechanism behind photo-induced reactions. Hydroxy-TEMP is a very specific redox probe for selectively identifying and quantifying singlet oxygen (O). In this work, the kinetics of radical generated by the oxidation products of the Hydroxy-TEMP redox probe was analyzed from EPR spectra in aqueous solutions of several water-soluble porphyrins (HT4MPyP, Na[HT4SPP], HT2MPyP, ZnT4MyPyP, MnT4MyPyP, HT4CPP, and HT4TriMAPP4) under white light illumination. Different factors such as the concentration of the redox probe, pH of the medium, and photostability of the porphyrins were evaluated. A systematic study was carried out to reveal the factors associated with stable radical degradation (TEMPOL) by illumination in the visible spectral region in systems containing photosensitizer (porphyrin) and redox probe (Hydroxy-TEMP). With the aid of EPR and gas chromatography coupled with mass spectroscopy (GC-MS) techniques, the mechanism of the radical degradation and the photobleaching of porphyrins were investigated. After successive interactions with the porphyrin in its excited state, in alkaline aqueous solution (pH > 10), the free radical TEMPOL is transformed into TEMPONE until the final diamagnetic product Phorone. A protocol was elaborated to identify and quantify the generation of O by Hydroxy-TEMP reliably, to avoid possible errors in the interpretation of efficiency of photosensitizers.
自旋陷阱和氧化还原探针的使用结合电子顺磁共振（EPR）是一种常用于评估涉及活性氧物种的光疗和光催化过程中光敏剂和光催化剂效率的方法。通过这种方式，该方法有助于阐明光诱导反应背后的机制。羟基-TEMP 是一种非常特定的氧化还原探针，可用于选择性识别和定量单线态氧（O）。在这项工作中，从几种水溶性卟啉（[HT4MPyP]（OTs）、Na[HT4SPP]、[HT2MPyP]（OTs）、[ZnT4MyPyP]（OTs）、[MnT4MyPyP]（OTs）、HT4CPP 和[HT4TriMAPP]（OTs）4）水溶液的 EPR 光谱中分析了氧化产物产生的自由基的动力学。评估了氧化还原探针的浓度、介质的 pH 值和卟啉的光稳定性等不同因素。进行了系统研究，以揭示与在含有光敏剂（卟啉）和氧化还原探针（羟基-TEMP）的系统中在可见光谱区域进行光照相关的稳定自由基降解（TEMPOL）的因素。借助 EPR 和气相色谱-质谱联用（GC-MS）技术，研究了自由基降解和卟啉光漂白的机制。在碱性水溶液（pH>10）中，在其激发态与卟啉连续相互作用后，自由基 TEMPOL 转化为 TEMPONE，直到最终的抗磁性产物 Phorone。制定了一个方案来可靠地识别和定量羟基-TEMP 生成的 O，以避免在解释光敏剂效率时可能出现的错误。
