Benzothiazole-substituted benzofuroquinolinium dyes as new fluorescent probes for G-quadruplex DNA

• Dyes with new structural scaffold based on a benzothiazole–benzofuroquinoline core with the incorporation of an amino group.
• Application as a G-quadruplex fluorescent probe with excellent selectivity, sensitivity, and stability.
• High fluorescent quantum yields when the dyes bound with G-quadruplex DNA.
• New fluorescent dyes for living cell staining and imaging.

A series of new benzothiazole–benzofuroquinoline conjugates were designed and synthesized to enhance the performance for the application as a G-quadruplex fluorescent probe. All compounds were characterized and the selectivity, sensitivity, and stability of these dyes interacting with G-quadruplex were studied by using fluorescence titration, native PAGE experiments, FRET and CD analysis. Significant enhancement of fluorescent quantum yield was observed when the compound bound with HRAS G-quadruplex. The results indicate that these compounds show much stronger binding affinity and fluorescent response to G-quadruplex than our previously reported benzothiazole–benzofuroquinoline core scaffold (CYTO) due to the incorporation of a specific amino moiety. The application of these new compounds as a fluorescent agent for living cell imaging was also demonstrated.

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