As a recently identified higher-order quadruplex (G4) structure, the G4 dimer possesses unique structure and biological functions. In this work, we found accidentally that two tandem PW17 (one known G4-forming DNA) sequences can fold into a stable G4 dimer, and the G4 dimer can enhance dramatically the fluorescence intensity of thioflavin T (ThT). The G4 dimer/ThT fluorescence intensity is about ninefold that of the corresponding G4 monomer/ThT. Meanwhile, compared with the common G4/ThT system, G4 dimer/ThT exhibited more stable fluorescence emission in the media with various concentrations of Na⁺ and K⁺. On the basis of these findings, G4 dimer/ThT was used as a fluorescence indicator to construct one arched DNA probe for label-free detection of DNA. By incorporating a G4 dimer sequence in amplified products, we further designed one rolling circle amplification-based biosensing strategy to show the utility of this G4 dimer/ThT fluorescence indicator. This study demonstrates that dimeric G4 is an effective nucleic acid scaffold for lighting up ThT, showing promising applications in a label-free bioassay.

中文翻译：

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二聚体G-四链体：点亮硫黄素T的有效核酸支架

作为最近确定的高阶四重体（G4）结构，G4二聚体具有独特的结构和生物学功能。在这项工作中，我们意外地发现，两个串联的PW17（一个已知的形成G4的DNA）序列可以折叠成稳定的G4二聚体，而G4二聚体可以显着增强硫黄素T（ThT）的荧光强度。G4二聚体/ ThT荧光强度约为相应G4单体/ ThT的九倍。同时，与普通的G4 / ThT系统相比，G4二聚体/ ThT在具有不同浓度的Na ⁺和K ⁺的介质中表现出更稳定的荧光发射。。基于这些发现，G4二聚体/ ThT用作荧光指示剂，构建了一种用于无标记检测DNA的拱形DNA探针。通过在扩增产物中掺入G4二聚体序列，我们进一步设计了一种基于滚环扩增的生物传感策略，以显示该G4二聚体/ ThT荧光指示剂的实用性。这项研究表明二聚体G4是点亮ThT的有效核酸支架，在无标记生物测定中显示出有希望的应用。