Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland.
Int J Mol Sci. 2021 Jan 17;22(2):885. doi: 10.3390/ijms22020885.
The influence of the stable 2,2,6,6-tetramethylpiperidinyl--oxyl (TEMPO) nitroxide and its six C4-substituted derivatives, as well as two C3-substituted analogues of 2,2,5,5-tetramethylpyrrolidynyl--oxyl (PROXYL) nitroxide on the chosen fluoroquinolone antibiotics (marbofloxacin, ciprofloxacin, danofloxacin, norfloxacin, enrofloxacin, levofloxacin and ofloxacin), has been examined in aqueous solutions by UV absorption as well as steady-state and time-resolved fluorescence spectroscopies. The mechanism of fluorescence quenching has been specified and proved to be purely dynamic (collisional) for all the studied systems, which was additionally confirmed by temperature dependence experiments. Moreover, the selected quenching parameters-that is, Stern-Volmer quenching constants and bimolecular quenching rate constants-have been determined and explained. The possibility of electron transfer was ruled out, and the quenching was found to be diffusion-limited, being a result of the increase in non-radiative processes. Furthermore, as the chosen nitroxides affected the fluorescence of fluoroquinolone antibiotics in different ways, an influence of the structure and the type of substituents in the molecules of both fluoroquinolones and stable radicals on the quenching efficiency has been determined and discussed. Finally, the impact of the solvent's polarity on the values of bimolecular quenching rate constants has been explained. The significance of the project comes from many applications of nitroxides in chemistry, biology and industry.
稳定的 2,2,6,6-四甲基哌啶-1-氧基（TEMPO）氮氧自由基及其六个 C4-取代衍生物，以及 2,2,5,5-四甲基吡咯烷-1-氧基（PROXYL）氮氧自由基的两个 C3-取代类似物对选定的氟喹诺酮类抗生素（马波沙星、环丙沙星、达氟沙星、诺氟沙星、恩诺沙星、左氧氟沙星和氧氟沙星）在水溶液中的影响，通过紫外吸收以及稳态和时间分辨荧光光谱进行了研究。荧光猝灭的机制已被指定并证明对于所有研究的系统都是纯粹的动态（碰撞），这通过温度依赖实验进一步得到证实。此外，还确定并解释了选定的猝灭参数，即 Stern-Volmer 猝灭常数和双分子猝灭速率常数。排除了电子转移的可能性，并且猝灭是扩散限制的，这是由于非辐射过程的增加。此外，由于所选的氮氧自由基以不同的方式影响氟喹诺酮类抗生素的荧光，因此确定并讨论了氟喹诺酮类抗生素和稳定自由基分子中结构和取代基类型对猝灭效率的影响。最后，解释了溶剂极性对双分子猝灭速率常数值的影响。该项目的意义在于氮氧自由基在化学、生物学和工业中的许多应用。
