ABSTRACT Supramolecular complexation of two bio-thiols, homocysteine (Hcys) and cysteine (Cys), by cucurbit[7]uril (CB[7]) has been fully investigated by 1H NMR spectroscopy, mass spectrometry, isothermal titration calorimetry, and the results were further verified with computational investigations. NMR titration experimental results obviously indicate that the binding stoichiometry of CB[7] to Hcys is 1:1 and to Cys is 1:2 in aqueous solution. The binding constants and thermodynamic parameters associated with the complexation between CB[7] and the bio-thiols were determined by isothermal titration calorimetry. The energy-minimized structures of the supramolecular complexes of CB[7] with Hcys and Cys were determined and provide good agreement with the experimental results. The CB[7] cavity is sufficient to include the two Cys, but is unable to accommodate two Hcys due to steric hindrance. The differing binding abilities of Hcys and Cys in aqueous solution towards CB[7] host may lead to discriminate them. Graphical abstract

中文翻译：

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同型半胱氨酸和半胱氨酸与葫芦[7]脲的超分子络合

摘要 葫芦 [7] 脲 (CB[7]) 对两种生物硫醇、高半胱氨酸 (Hcys) 和半胱氨酸 (Cys) 的超分子络合已通过 1H NMR 光谱、质谱、等温滴定量热法进行了全面研究，结果通过计算研究进一步验证。NMR滴定实验结果明显表明CB[7]与Hcys的结合化学计量为1:1，与Cys在水溶液中的结合化学计量为1:2。通过等温滴定量热法测定与 CB[7] 和生物硫醇之间的络合相关的结合常数和热力学参数。CB[7] 与Hcys 和Cys 的超分子复合物的能量最小化结构被确定并且与实验结果具有很好的一致性。CB[7] 腔足以包含两个 Cys，但由于空间位阻无法容纳两个 Hcy。Hcys 和 Cys 在水溶液中对 CB[7] 宿主的不同结合能力可能导致区分它们。图形概要