Faculty of Chemistry, University of Wroclaw , Wroclaw, Poland.
Inorg Chem. 2013 Dec 16;52(24):13927-33. doi: 10.1021/ic401451s. Epub 2013 Dec 4.
2-Amino-2-hydroxymethyl-propane-1,3-diol, or tris(hydroxymethyl)aminomethane (Tris), is probably the most common biochemical buffer used alone or in combination with other buffers because it is stable, unreactive, and compatible with most proteins and other biomolecules. Being nontoxic, it has even found applications in medicine. Tris is known, however, to coordinate transition metal ions, Cu(II) among them. Although often ignored, this feature affects interactions of Cu(II) ions with biomolecules, as Tris is usually used in high molar excess. Therefore, it is important to have precise knowledge on the stoichiometry, stability, and reactivity of cupric Tris complexes. The literature data are incoherent in this respect. We reinvestigated the complex formation in the Tris-Cu(II) system by potentiometry, UV-vis, ESI-MS, and EPR at a broad range of concentrations and ratios. We found, contrary to several previous papers, that the maximum stoichiometry of Tris to Cu(II) is 2 and at neutral pH, dimeric complexes are formed. The apparent affinity of Tris buffer for Cu(II), determined by the competitivity index (CI) approach [Krężel, A.; Wójcik, J.; Maciejczyk, M.; Bal, W. Chem. Commun. 2003, 6, 704-705] at pH 7.4 varies between 2 × 10(6) and 4 × 10(4) M(-1), depending on the Tris and Cu(II) concentrations and molar ratio.
2-氨基-2-羟甲基丙烷-1,3-二醇，或三羟甲基氨基甲烷（Tris），可能是最常用的单独或与其他缓冲液组合使用的生化缓冲液，因为它稳定、无反应性，并且与大多数蛋白质和其他生物分子兼容。由于它无毒，甚至在医学中也有应用。然而，Tris 已知可以与过渡金属离子配位，其中包括 Cu(II)。尽管通常被忽略，但这个特性会影响 Cu(II)离子与生物分子的相互作用，因为 Tris 通常以高摩尔过量使用。因此，准确了解铜三嗪配合物的化学计量、稳定性和反应性非常重要。文献数据在这方面不一致。我们通过电位法、UV-vis、ESI-MS 和 EPR 在广泛的浓度和比例范围内重新研究了 Tris-Cu(II)系统中的配合物形成。我们发现，与之前的几篇论文相反，Tris 与 Cu(II)的最大配合物化学计量比为 2，并且在中性 pH 下形成二聚体配合物。通过竞争指数（CI）方法[Krężel, A.; Wójcik, J.; Maciejczyk, M.; Bal, W. Chem. Commun. 2003, 6, 704-705]确定的 Tris 缓冲液对 Cu(II)的表观亲和力在 pH 7.4 时在 2×10(6)和 4×10(4) M(-1)之间变化，具体取决于 Tris 和 Cu(II)的浓度和摩尔比。
