The polymorphic formation of G-quadruplex brings more attentions, because changes of formation sites affect many physiological processes, like telomere maintenance, transcription and DNA replication. These processes are highly susceptible to ROS-induced oxidative damage. In this work, bichromophoric cores of symmetric squaraine probe linked with ether chain is conducive to the recognition of G-quadruplex, based on the mechanism of intra or intermolecular “aggregation-disaggregation”. Several interaction behaviors, such as self-aggregation, binding affinity, stoichiometric ratio, were fully investigated via spectrum titration, circular dichroism, fluorescent intercalator displacement assay, and molecular docking. Furthermore, tracking G-quadruplex distribution in the cytoplasm was monitored by during the oxidative stress enhancement. Interestingly, the G-quadruplex levels in the cytoplasm of cancer cells were slightly higher than that of normal cells to deal with oxidation-reduction imbalance. Overall, the lower detection limit of for parallel G-quadruplex like pu27 is as low as 7.2 nM; and the complex of and G-quadruplex will not change the topological structure of G-quadruplex. It has good sensitive and stability for parallel type of G-quadruplex. It is a potential tool for bioimaging of G-quadruplex in the cytoplasm.

中文翻译：

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基于双发色方酸的近红外荧光探针，用于活细胞中的 G-四链体


G-四链体的多态性形成引起了更多的关注，因为形成位点的变化影响许多生理过程，如端粒维持、转录和DNA复制。这些过程非常容易受到 ROS 诱导的氧化损伤的影响。在这项工作中，基于分子内或分子间“聚集-解聚”的机制，对称方酸菁探针的双发色核心与醚链连接有利于G-四链体的识别。通过光谱滴定、圆二色性、荧光嵌入剂置换分析和分子对接，充分研究了自聚集、结合亲和力、化学计量比等多种相互作用行为。此外，在氧化应激增强期间追踪细胞质中的 G-四链体分布。有趣的是，癌细胞细胞质中的G-四链体水平略高于正常细胞，以应对氧化还原失衡。总体而言，像 pu27 这样的平行 G 四链体的检测下限低至 7.2 nM；和G-四联体的复合物不会改变G-四联体的拓扑结构。对于平行型G-四链体具有良好的灵敏度和稳定性。它是细胞质中 G-四链体生物成像的潜在工具。