Abstract：
4-(2-Pyridylazo)resorcinol (PAR) is one of the most popular chromogenic chelator used in the determination of the concentrations of various metal ions from the d, p and f blocks and their affinities for metal ion-binding biomolecules. The most important characteristics of such a sensor are the molar absorption coefficient and the metal-ligand complex dissociation constant. However, it must be remembered that these values are dependent on the specific experimental conditions (e.g. pH, solvent components, and reactant ratios). If one uses these values to process data obtained in different conditions, the final result can be under- or overestimated. We aimed to establish the spectral properties and the stability of PAR and its complexes accurately with Zn(2+), Cd(2+), Hg(2+), Co(2+), Ni(2+), Cu(2+), Mn(2+) and Pb(2+) at a multiple pH values. The obtained results account for the presence of different species of metal-PAR complexes in the physiological pH range of 5 to 8 and have been frequently neglected in previous studies. The effective molar absorption coefficient at 492 nm for the ZnHx(PAR)2 complex at pH7.4 in buffered water solution is 71,500 M(-1) cm(-1), and the dissociation constant of the complex in these conditions is 7.08×10(-13) M(2). To confirm these values and estimate the range of the dissociation constants of zinc-binding biomolecules that can be measured using PAR, we performed several titrations of zinc finger peptides and zinc chelators. Taken together, our results provide the updated parameters that are applicable to any experiment conducted using inexpensive and commercially available PAR.
摘要：
4-（2-吡啶偶氮）间苯二酚（PAR）是最受欢迎的显色螯合剂之一，用于测定各种金属离子的浓度，p和f嵌段及其对金属离子结合生物分子的亲和力。这种传感器最重要的特性是摩尔吸光系数和金属-配体络合物解离常数。然而,必须记住，这些值取决于特定的实验条件(例如pH，溶剂组分,和反应物比例)。如果使用这些值处理在不同条件下获得的数据，最终结果可能被低估或高估。我们旨在建立PAR及其配合物与Zn(2+)的光谱性质和稳定性,Cd(2+),Hg(2+),Co(2+),Ni(2+),Cu(2+),Mn(2+)和Pb(2+)在多个pH值下。获得的结果说明了在5至8的生理pH范围内存在不同种类的金属-PAR配合物，并且在先前的研究中经常被忽略。在缓冲水溶液中，pH7.4时ZnHx（PAR）2络合物在492nm处的有效摩尔吸光系数为71,500M（-1）cm（-1），在这些条件下配合物的解离常数为7.08×10(-13)M(2)。为了确认这些值并估计可以使用PAR测量的锌结合生物分子的解离常数的范围，我们对锌指肽和锌螯合剂进行了多次滴定。一起来看,我们的结果提供了适用于使用廉价且市售PAR进行的任何实验的更新参数.
