Department of Chemistry, New York University, New York, NY 10003, USA.
J Mol Recognit. 2012 Apr;25(4):234-7. doi: 10.1002/jmr.2183.
DNA is a highly effective molecule for controlling nanometer-scale structure. The convenience of using DNA lies in the programmability of Watson-Crick base-paired secondary interactions, useful both to design branched molecular motifs and to connect them through sticky-ended cohesion. Recently, the tensegrity triangle motif has been used to self-assemble three-dimensional crystals whose structures have been determined; sticky ends were reported to be the only intermolecular cohesive elements in those crystals. A recent communication in this journal suggested that tertiary interactions between phosphates and cytosine N(4) groups are responsible for intermolecular cohesion in these crystals, in addition to the secondary and covalent interactions programmed into the motif. To resolve this issue, we report experiments challenging this contention. Gel electrophoresis demonstrates that the tensegrity triangle exists in conditions where cytosine-PO(4) tertiary interactions seem ineffective. Furthermore, we have crystallized a tensegrity triangle using a junction lacking the cytosine suggested for involvement in tertiary interactions. The unit cell is isomorphous with that of a tensegrity triangle crystal reported earlier. This structure has been solved by molecular replacement and refined. The data presented here leave no doubt that the tensegrity triangle crystal structures reported earlier depend only on base pairing and covalent interactions for their formation.
DNA 是一种控制纳米级结构的高效分子。使用 DNA 的便利性在于 Watson-Crick 碱基配对的二级相互作用的可编程性，这对于设计分支分子基序和通过粘性末端的内聚来连接它们都很有用。最近，张力三角形基序已被用于自组装三维晶体，其结构已被确定；粘性末端被报道是这些晶体中唯一的分子间内聚元素。该杂志的一篇最新通讯表明，除了基序中编入的二级和共价相互作用外，磷酸基团和胞嘧啶 N(4) 基团之间的三级相互作用负责这些晶体中的分子间内聚。为了解决这个问题，我们报告了挑战这一论点的实验。凝胶电泳表明，在似乎没有胞嘧啶-PO(4)三级相互作用的条件下，张力三角形存在。此外，我们使用缺乏被认为参与三级相互作用的胞嘧啶的连接点结晶了一个张力三角形。该单元与之前报道的张力三角形晶体的单元相同。该结构通过分子置换和精炼得到解决。这里呈现的数据毫无疑问地表明，之前报道的张力三角形晶体结构仅依赖于碱基配对和共价相互作用形成。
