Live-Cell Imaging of RNA G-Quadruplex with a Dual-Color Fluorescence Switch-on Probe

In-cell imaging of the G-quadruplex (G4) formation of nucleic acids remains challenging for revealing G4's functions in cells. This study describes the cell imaging method of G4 nucleic acids using our unique tripodal quinone-cyanine fluorescent dye, QCy(MeBT)₃, whose 600 nm and 700 nm fluorescence is enhanced independently upon the binding with double-stranded DNA and G4-DNA/RNA, respectively. The use of QCy(MeBT)₃ enables us to visualize cytosolic G4 RNAs in fixed and living HeLa cells with near-infrared 700 nm fluorescence.