During the preparation of single-stranded DNA catenanes, topological isomers of different linking numbers (Lk) are intrinsically produced, and they must be separated from each other to construct sophisticated nanostructures accurately. In many previous studies, however, mixtures of these isomers were directly employed to construct nanostructures without sufficient characterization. Here, we present a method that easily and clearly characterizes the isomers by polyacrylamide gel electrophoresis. To the mixtures of topological isomers of [2]catenanes, two-strut oligonucleotides, which are complementary with a part of both rings, were added to connect the rings and fix the whole conformations of isomers. As a result, the order of migration rate was always Lk3 > Lk2 > Lk1, irrespective of gel concentration. Thus, all the topological isomers were unanimously characterized by only one polyacrylamide gel electrophoresis experiment. Well-characterized DNA catenanes are obtainable by this two-strut strategy, opening the way to more advanced nanotechnology.

中文翻译：

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轻松表征 DNA 链的拓扑结构

在制备单链 DNA 链环的过程中，本质上会产生不同连接数 (Lk) 的拓扑异构体，它们必须相互分离才能准确构建复杂的纳米结构。然而，在之前的许多研究中，这些异构体的混合物被直接用于构建纳米结构，而没有充分表征。在这里，我们提出了一种通过聚丙烯酰胺凝胶电泳轻松清晰地表征异构体的方法。在[2]链的拓扑异构体混合物中，加入与两个环的一部分互补的双支柱寡核苷酸以连接环并固定异构体的整个构象。因此，无论凝胶浓度如何，迁移率的顺序始终为 Lk3 > Lk2 > Lk1。因此，所有拓扑异构体仅通过一次聚丙烯酰胺凝胶电泳实验得到一致表征。通过这种双支柱策略可以获得表征良好的 DNA 链，为更先进的纳米技术开辟了道路。