Effect of BSA binding on photophysical and photochemical properties of triarylmethane dyes
Effect of BSA binding on photophysical and photochemical properties of triarylmethane dyes
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DOI：
10.1021/jp981185n
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发表时间：
1998-06-04
影响因子：
3.3
通讯作者：
Indig, GL
中科院分区：
文献类型：
--
作者：
Baptista, MS;Indig, GL
我们采用稳态和时间分辨光谱技术相结合来探索蛋白质结合对三种三芳基甲烷染料（乙基紫、结晶紫和孔雀石绿）的光物理和光化学性质的影响。我们的结果表明，牛血清白蛋白（BSA）的结合位点对于防止通过这些三芳基甲烷的芳环的旋转运动而发生的快速非辐射弛豫过程非常有效。结果，在蛋白质结合后观察到荧光量子产率和寿命、系统间交叉效率和光反应性显着增强。对与 BSA 非共价结合的乙基紫进行 532 nm 激光诱导光漂白，产生无色乙基紫和 4,4'-双（二乙氨基）二苯甲酮作为反应产物。前者在氮气吹扫的样品中更为突出，后者在空气平衡的样品中更为突出。乙基紫络合物的时间分辨瞬态光谱显示乙基紫三重态和半还原染料自由基的光谱特征的叠加元素。根据反应光产物和瞬时中间体的性质，漂白过程的第一步被假设为电子或氢原子从蛋白质转移到染料部分。对于蛋白质结合的结晶紫观察到类似的反应机制。
We have employed a combination of steady-state and time-resolved spectroscopic techniques to explore the effect of protein binding on the photophysical and photochemical properties of three triarylmethane dyes: ethyl violet, crystal violet, and malachite green. Our results indicate that the binding sites of bovine serum albumin (BSA) are very efficient in preventing fast nonradiative relaxation processes that occur via rotational motion of the aromatic rings of these triarylmethanes. As a result, remarkable enhancements in fluorescence quantum yield and lifetime, intersystem crossing efficiency, and photoreactivity are observed upon protein binding. The 532 nm laser-induced photobleaching of ethyl violet noncovalently bound to BSA yields leuco ethyl violet and 4,4'-bis(diethylamino)benzophenone as reaction products. The former was more prominent in nitrogen-purged samples and the latter in air-equilibrated samples. The time-resolved transient spectra of the ethyl violet complex show superimposed elements of the spectroscopic signatures of both ethyl violet triplet and the semireduced dye radical. Based on the nature of the reaction photoproducts and transient intermediates, the first step of the bleaching process is postulated to be an electron or hydrogen atom transfer from the protein to the dye moiety. An analogous reaction mechanism was observed for protein-bound crystal violet.