Fluorescently Sensing of DNA Triplex Assembly Using an Isoquinoline Alkaloid as Selector,Stabilizer, Inducer,and Switch‐On Emitter

DNA triplex assembly has attracted a variety of interest in the regulation of genetic expression, drug screening, molecular switches, and sensors. However, these achievements are essentially dependent on the formation and stability of the triplex assembly. Herein, the recognition of DNA triplex assembly with various isoquinoline alkaloids was investigated. We found that natural chelerythrine (CHE) exhibits the highest selectivity in recognizing the triplex structure. The DNA triplex stability is substantially increased upon CHE binding, as opposed to the invariance in the stability of the duplex counterpart. CHE also favors the assembly of the triplex‐forming oligonucleotide (TFO) with its duplex counterpart. The triplex binding switches CHE to a strong fluorescent emitter, which suggests CHE as a useful probe in following triplex assembly. As a unique triplex selector, inducer, and emitter, CHE successfully reports the wide pH‐ and metal‐ion‐dependent tunability of the triplex nanoswitch in a label‐free manner.