Nonlinear optical dye TSQ1 as an efficiently selective fluorescent probe for G-quadruplex DNA

A squarylium dye TSQ1 shows a remarkable fluorescence enhancement selectivity for the G-quadruplex DNA structure against duplex DNA, it can be distinguished even by the naked eye. What is more important, TSQ1 did not induce the G-rich sequence folding into G-quadruplex structure which means TSQ1 can be used to detect G-quadruplex structures in cells.