Stoichiometry between Humate Unit Molecules and Metal ions in Supramolecular Assembly Induced by Cu2+ and Tb3+ Measured by Gel Electrophoresis Techniques
Stoichiometry between Humate Unit Molecules and Metal ions in Supramolecular Assembly Induced by Cu2+ and Tb3+ Measured by Gel Electrophoresis Techniques
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凝胶电泳技术测量 Cu2 和 Tb3 诱导的超分子组装中腐植酸单元分子与金属离子的化学计量
DOI：
10.1021/acs.est.1c03993
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发表时间：
2021
影响因子：
11.4
通讯作者：
Shingo Saito
中科院分区：
文献类型：
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作者：
Sumika Nakano;Kazuki Marumo;Rintaro Kazami;Takumi Saito;Tomoko Haraga;Yuiko Tasaki-Handa;Shingo Saito
腐植酸(HA)是腐植酸类物质的一种，它能通过配位结合等分子间作用力与金属离子强烈络合，形成超分子组装。然而，确定组成HA超分子的小分子单位分子与金属离子之间的超分子尺寸分布和化学计量比已被证明是具有挑战性的。在这里，我们研究了Cu2+和Tb3+离子对HA络合物和结合的金属离子的分离和定量的影响，然后用UV-Vis光谱和激发发射矩阵平行因子分析研究了Cu2+和Tb3+离子诱导的HAS的尺寸分布的变化。通过测定HA和金属离子的浓度，可以估算HA单元分子对超分子络合物中金属离子的化学计量比。从泥炭(PAHA)和深层地下水(HHA)中采集的腐植酸与Cu2+、Tb3+形成的超分子络合物具有不同的超分子行为。例如，在Cu2+-HHA的情况下，两个HHA单元分子通过Cu2+离子的交联形成超分子。我们的结果表明，这种超分子化学计量比与HHA元素组成中硫原子的丰度有关。我们的实验结果和分析为通过金属络合形成的HA超分子提供了新的见解。
Humic acid (HA), a fraction of humic substances, can strongly complex with metal ions to form a supramolecular assembly via coordination binding and other intermolecular forces. However, determining the supramolecular size distribution and stoichiometry between small HA unit molecules constituting HA supramolecules and metal ions has proven to be challenging. Here, we investigated the changes in the size distributions of HAs induced by Cu2+and Tb3+ions using unique PAGE for the separation and quantification of HA complexes and metal ions bound, followed by UV–vis spectroscopy and excitation–emission matrix–parallel factor analysis. By determining the concentrations of HA and metal ions, it was possible to estimate the stoichiometry of the HA unit molecule to metal ions in supramolecular complexes. It was found that the supramolecular behaviors of Cu2+and Tb3+complexes with HA collected from peat (PAHA) and deep groundwater (HHA) differed. For example, two HHA unit molecules form a supramolecule via cross-linking by a Cu2+ion in the case of Cu2+–HHA. Our results suggest that this supramolecular stoichiometry is related to the abundance of sulfur atoms in the elemental composition of HHA. Our experimental results and analysis provide new insights into HA supramolecules formed via metal complexation.