One colorimetric and one fluorescent-indicator displacement assay (IDA) were studied to assess their interaction with methyl viologen (MV), an herbicide commercially known as paraquat. The host–guest complexes formed by cucurbit[7]uril (CB[7]) and the 4-nitroaniline (NA) or Berberine (Be) dyes function as colorimetric- and fluorescent-IDA for MV, respectively. The CB[7]@NA and CB[7]@Be complexes were characterized by UV–vis, fluorescence spectroscopy, and dynamic simulations. Isothermal titration calorimetry (ITC) experiments and dynamic simulations were employed to obtain thermodynamic data for the formation of the 1:1 inclusion complexes. Finally, NA is proposed as a reference colorimetric dye for determining CB[7]-binding affinities using competitive host–guest titrations, and the fluorescent-IDA as the best assay proposed, as it exhibits a high binding constant, a good detection limit of 2.7 × 10⁻⁶ mol L^-1, good linearity in the range from 4 × 10⁻⁶ mol L^-1 to 3.5 × 10⁻⁵ mol L^-1, in aqueous solution.

中文翻译：

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基于葫芦[7]脲的甲基紫精指示剂置换测定的比较研究。理论和实验的视角

研究了一种比色法和一种荧光指示剂置换测定 (IDA)，以评估它们与甲基紫精 (MV) 的相互作用，甲基紫精是一种商业上称为百草枯的除草剂。由葫芦[7]脲（CB[7]）和4-硝基苯胺（NA）或小檗碱（Be）染料形成的主客体复合物分别充当MV的比色IDA和荧光IDA。通过紫外-可见光、荧光光谱和动态模拟对 CB[7]@NA 和 CB[7]@Be 配合物进行了表征。采用等温滴定量热法 (ITC) 实验和动态模拟来获得 1:1 包合物形成的热力学数据。最后，NA 被建议作为参考比色染料，用于使用竞争性主客体滴定来确定 CB[7] 结合亲和力，并且荧光 IDA 作为建议的最佳检测方法，因为它表现出高结合常数、良好的检测限2.7 × 10 ^-6  mol L ^{-1 ，在4 × 10 -6}  mol L ^-1至3.5 × 10 ^-5  mol L ^-1范围内线性良好，在水溶液中。