I-motif DNAs have been widely employed as robust modulating components to construct reconfigurable DNA nanodevices that function well in acidic cellular environments. However, they generally display poor interactivity with fluorescent ligands under these complex conditions, illustrating a major difficulty in utilizing i-motifs as the light-up system for label-free DNA nanoassemblies and bioimaging. Towards addressing this challenge, here we devise new types of i-motif/miniduplex hybrid structures that display an unprecedentedly high interactivity with commonly-used benzothiazole dyes (e.g. thioflavin T). A well-chosen tetranucleotide, whose optimal sequence depends on the used ligand, is appended to the 5'-terminals of diverse i-motifs and forms a minimal parallel duplex thereby creating a preferential site for binding ligands, verified by molecular dynamics simulation. In this way, the fluorescence of ligands can be dramatically enhanced by the i-motif/miniduplex hybrids under complex physiological conditions. This provides a generic light-up system with a high signal-to-background ratio for programmable DNA nanoassemblies, illustrated through utilizing it for a pH-driven framework nucleic acid nanodevice manipulated in acidic cellular membrane microenvironments. It enables label-free fluorescence bioimaging in response to extracellular pH change.

中文翻译：

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I-Motif / miniduplex杂化结构以前所未有的效率结合苯并噻唑染料：用于无标记DNA纳米组件和生物成像的通用照明系统。

I-基序DNA已被广泛用作鲁棒的调节成分，以构建在酸性细胞环境中功能良好的可重构DNA纳米器件。但是，它们通常在这些复杂条件下与荧光配体的相互作用较弱，这说明利用i-基序作为无标记DNA纳米组件和生物成像的照明系统存在重大困难。为了应对这一挑战，我们在这里设计了新型的i-基序/微双链杂化结构，该结构与常用的苯并噻唑染料（例如硫黄素T）具有空前的高相互作用。一种精心选择的四核苷酸，其最佳序列取决于所用的配体，它附着在各种i-基序的5'末端，并形成最小的平行双链体，从而为结合配体创造了优先位点，通过分子动力学仿真验证。以此方式，在复杂的生理条件下，i-基序/微型双链体杂合体可以显着增强配体的荧光。这为可编程DNA纳米组件提供了一种具有高信噪比的通用照明系统，通过将其用于在酸性细胞膜微环境中操纵的pH驱动框架核酸纳米器件来说明。它可以响应细胞外pH值变化而进行无标记的荧光生物成像。通过将其用于在酸性细胞膜微环境中操作的pH驱动框架核酸纳米装置进行了图解说明。它可以响应细胞外pH值变化而进行无标记的荧光生物成像。通过将其用于在酸性细胞膜微环境中操作的pH驱动框架核酸纳米装置进行了图解说明。它可以响应细胞外pH值变化而进行无标记的荧光生物成像。