Aqueous coordination chemistry of quinoline-based fluorescence probes for the biological chemistry of zinc
Aqueous coordination chemistry of quinoline-based fluorescence probes for the biological chemistry of zinc
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DOI：
10.1021/ja992709f
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发表时间：
1999-12-15
影响因子：
15
通讯作者：
O'Halloran, TV
中科院分区：
文献类型：
--
作者：
Fahrni, CJ;O'Halloran, TV
金属特异性荧光探针在理解锌的神经生物学和一般细胞生物学方面越来越重要。TSQ和zinquin等几种基于喹啉的化合物已被用于在体内荧光显微镜实验中检测锌;然而，水溶液的化学性质仍然不明确。在某些情况下，该系列探针据说可以揭示细胞内不稳定的Zn（II）池，但在其他情况下，这些探针被认为可以从蛋白质中紧密结合的位点去除Zn（II）。由于锌-锌醌在水溶液中相互作用的结合模式、配位数和热力学尚未建立，这些建议很难区分。在这里，我们表明，在生理条件下，各种形式的zinquin绑定锌（II）具有高度的cooperativity形成2：1复合物。电位法、紫外-可见光法和荧光法在生理条件下均产生log K = 13.5的总体结合常数。为了把这个数字与其他锌螯合剂和生物配体的角度来看，我们比较了计算出的所谓的pM值（-log[Zn（II）]（自由））的一系列化合物在一个典型的条件下具有不同的化学计量。锌喹的pZn值（9.3）与EGTA相似。(9.5)但远小于碳酸酐酶（12.4）或EDTA（14.3）的值，因此可以作为比较锌亲和力的有用指标。相对于在体内应用的zinquin，如细胞内荧光显微镜研究，我们结束，在水溶液中的游离锌（II）的典型检测限为4 phl，或0.3万亿分之一，在pH 7.2。这些结果对锌在各种细胞内隔室中的可用性具有影响。
Metal-specific fluorescence probes are of increasing importance in understanding the neurobiology and general cell biology of zinc. Several quinoline-based compounds such as TSQ and zinquin have been employed to detect zinc in fluorescence microscopy experiments in vivo; however, the aqueous solution chemistry remains equivocal. In some cases, this family of probes is said to reveal labile pools of Zn(II) inside the cell, yet in other cases, these probes ate suggested to remove Zn(II) from tightly bound sites in proteins. Since the binding modes, coordination numbers, and thermodynamics of zinc-zinquin interactions in aqueous solution have not been established, these proposals are difficult to distinguish. Here we show that, under physiological conditions, the various forms of zinquin bind Zn(II) with a high degree of cooperativity forming 2:1 complexes. Potentiometric, UV-visible, and fluorescence methods all yield an overall binding constant of log K = 13.5 under physiological conditions. To put this number in perspective with other Zn chelators and biological ligands, we compare the calculated so-called pM values (-log[Zn(II)](free)) for a series of compounds with different stoichiometries under a typical condition. The pZn value for zinquin (9.3) is similar to that of EGTA. (9.5) but much smaller than the value for carbonic anhydrase (12.4) or EDTA (14.3) and, thus, serves as a useful gauge for comparing zinc affinities. With respect to in vivo applications of zinquin, such as intracellular fluorescence microscopy studies, we End that the typical detection limit for free Zn(II) in aqueous solution is 4 phl, or 0.3 parts per trillion, at pH 7.2. These results have implications for the availability of zinc in various intracellular compartments.