Feng Tingting, Grusenmeyer Tod A, Lupin Max, Schmehl Russell H
Department of Chemistry, Tulane University, New Orleans, LA.
Photochem Photobiol. 2015 May-Jun;91(3):705-13. doi: 10.1111/php.12381. Epub 2014 Nov 28.
This work reports an examination of singlet oxygen reactions with amino acid substrates by a method involving measurement of the change in phosphorescence intensity of the singlet oxygen sensitizer. The sensitizer, a Ru(II) bipyridyl complex covalently linked to pyrene, has long-lived phosphorescence in N2 purged aqueous solutions (τ0 ~ 20 μs) that is nearly completely quenched by oxygen in aerated solutions. Irradiation of the complex in water containing sub mM concentrations of histidine, tryptophan and methionine results in a dramatic, easily visible increase in the phosphorescence intensity over a period of 10-100 s. Rate constants for singlet oxygen oxidation of each of the substrates can be obtained by using changes in the phosphorescence intensity in initial rate kinetic analysis. Rate constants obtained in this way compare favorably with those reported in the literature. The method represents a very simple approach for obtaining rate constants for singlet oxygen reactions with various substrates and the kinetics can be extended to nonaqueous solvents.
本研究报告了一种通过测量单线态氧敏化剂磷光强度变化的方法来检测单线态氧与氨基酸底物的反应。该敏化剂是一种与芘共价连接的Ru(II)联吡啶配合物，在氮气吹扫的水溶液中具有长寿命磷光（τ0约为20μs），在曝气溶液中几乎完全被氧气淬灭。在含有亚毫摩尔浓度组氨酸、色氨酸和甲硫氨酸的水中照射该配合物，会在10 - 100秒内使磷光强度显著且易于观察到地增加。通过在初始速率动力学分析中使用磷光强度的变化，可以获得每种底物的单线态氧氧化速率常数。以这种方式获得的速率常数与文献报道的结果相当。该方法是获得单线态氧与各种底物反应速率常数的一种非常简单的方法，并且动力学可以扩展到非水溶剂。
