Quencher as leaving group: efficient detection of DNA-joining reactions.

We describe a new fluorescence reporting strategy in which dabsyl, a well-known quencher, activates a hydroxyl group in a probe to convert it to a leaving group. When a nucleophilic phosphorothioate probe binds adjacent to a dabsyl quenched probe, autoligation occurs, releasing the quencher, and lighting up the probes, This signal change can be used to detect single nucleotide differences in DNA without enzymes or reagents.