Black Hole Quenchers are a series of dark quenchers developed by Biosearch Technologies in Novato, California. Dark Quenchers are commonly paired with fluorescent dyes to enhance the observable change in fluorescence. Carefully designed experiments or assays enable scientists to associate this observable change in fluorescence with a biochemical change.

BHQ molecules have a polyaromatic-azo backbone which makes the dyes nonfluorescent. The absorption spectra are tuned through electron-donating and -withdrawing substituents on the aromatic rings. In this way, a series of BHQ dyes’ absorption spectra are able to overlap with the emission spectra of common reporter dyes to maximize FRET quenching. In addition, the BHQs have been shown to efficiently engage in static quenching via a ground state complex.

The BHQ dyes can be used to label oligonucleotides via CPGs and amidites; while BHQ acids and esters can be used to label peptides and other biomolecules.
{| class="wikitable"
|-
! Black Hole Quenchers
! Absorption λ_(max)
! FRET Quenching Range
|-
| BHQ-1
| 534 nm
| ~480 - 580 nm
|-
| BHQ-2
| 579 nm
| ~559 - 670 nm
|-
| BHQ-3
| 680 nm
| ~620 - 730 nm
|}

References

M.K. Johansson, R.M. Cook, Chem. Eur. J. 2003, 9, 3466-3471.

Marras, S. A. E., Russell, F.R., and Tiyagi. S. Efficiencies of Fluorescence energy transfer and contact-mediated quenching in oligonucleotide probes. Nucleic Acid Resarch. '2002, 30. e122.

Reynisson, E., M. H. Josefsen, M. Krause, and J. Hoorfar. 2006. Evaluation of probe chemistries and platforms to improve the detection limit of real-time PCR. J Microbiol Methods 66:206-216.