Quencher

A quencher, in chemistry and biochemistry, is a molecule capable of reducing or silencing the signal produced by a nearby reporter, typically a fluorophore. Quenching can occur through energy transfer, collisional interactions, or complex formation, and is exploited in assays to control when signals appear.

In fluorescence-based molecular biology methods, quenchers are paired with reporter dyes in probes and adapters. When the probe is intact, the quencher suppresses fluorescence; during signal-generating steps, such as cleavage or separation, the reporter is freed from the quencher and fluorescence increases. Common examples include dark quenchers such as Dabcyl, Iowa Black FQ, BHQ-1, BHQ-2, and BHQ-3.

Mechanisms include Förster resonance energy transfer (FRET), dynamic (collisional) quenching in the excited state, and static quenching via ground-state complex formation. Quenching efficiency depends on spectral overlap, the distance between donor and quencher, and the specific quenching mechanism involved.

Outside fluorescence, quenching can refer to deactivating reactive species in chemical reactions. In metallurgy and related fields, the medium used to cool a hot workpiece is called a quenchant rather than a quencher. In standard biochemical contexts, however, the term quencher primarily denotes molecules that suppress fluorescence or other signals, enabling controlled measurement or signaling.