G-quadruplex fluorescence quenching ability: a simple and efficient strategy to design a single-labeled DNA probe

A single labeled fluorescence probe was designed based on the efficient quenching ability of a G-quadruplex instead of traditional quenchers. Using this probe, we have investigated the quenching ability of a G-quadruplex and developed a new approach to analyze mercury ions and cysteine with high specificity and sensitivity. Owing to the high quenching ability of the G-quadruplex and the fidelity of the "thymine–Hg2+–thymine" binding motif, this approach can detect 4.0 nM mercury ions, which is lower than the 10 nM US EPA limit in drinking water.