Black Hole Quencher (BHQ) dyes

Trust the original Black Hole Quenchers™ by the original manufacturer.

BHQ product lineSince 2000, Black Hole Quencher (BHQ™) dyes have served as the quencher of choice for qPCR probes and other fluorescence-quenched probe applications.

They remain the most widely used and validated dark quencher on the market, with more than 10,000 product citations and near ubiquitous use in molecular diagnostics and agricultural assays.


  • Six out of seven of the World Health Organization’s COVID-19 testing protocols use BHQ dyes.
  • The top ten molecular diagnostic manufacturers leverage BHQ technology in their assays.


BHQ dyes are efficient, true dark quenchers with no fluorescent signal. Through a combination of FRET and static quenching, they deliver results without the residual background signal common to other quenchers. 


Black Hole Quencher Dual-labeled Probes

Every qPCR probe format is available as an oligo labeled with a BHQ dye. In addition, each oligo may be labeled with a variety of other fluorophores such as FAM, TET, HEX, JOE, CAL Fluor™ and Quasar™ dyes.

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Black Hole Quencher oligonucleotide synthesis reagents 

Black Hole Quenchers are available for purchase for synthesizing dual-labeled oligonucleotides. Our BHQ dyes are available for 3’, internal and 5’ modifications. We also offer Black Hole Quenchers for labeling peptides. Our BHQ dyes are also available as carboxylic acid or succinimidyl esters, and as FMOC lysine conjugates.

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Versatile quenchers, flexible applications

The ideal combination of fluorophore and respective BHQ quencher yields a high signal-to-noise ratio and superior data quality that benefits a range of applications. The dyes simplify the design, implementation, and interpretation of qPCR assays, including COVID-19 detection assays. They are also integral to assays that query single and multiplex gene expression, copy number variation, SNP genotyping and presence/absence. This includes Biosearch Technologies’ own COVID-19 variant surveillance genotyping assays.

Depending on the application, BHQ dyes have broad absorption spectra spanning 480-580 nm (BHQ-1), 559-670 nm (BHQ-2) and 620-730 nm (BHQ-3). This versatility means our dyes can be paired with a wide range of fluorophores in multiplexed assay designs, including FAM, TET, HEX, JOE, CAL Fluor and Quasar dyes. Use our easy-to-use Spectral Overlay Tool to find the right dye for your assay.

BHQ dyes are used for sensitive imaging and detection in a diverse range of research from in vivo monitoring of glucose and insulin to tracking signal pathway activation. Read more on the Biosearch Technologies Blog

BHQ product lineA single-source supply chain

We develop and manufacture our own dyes, meaning we have a secure supply chain and rigorous quality control for these vital raw materials. We are our own supplier. This reliability means researchers can be confident in their ability to scale up and advance their manufacturing and distribution. That’s one of the reasons why so many top assay manufactures rely on Biosearch Technologies and BHQ dyes for critical COVID-19 assays.


Leverage our experience to design your own oligos

BHQ dyes are the only dark quenchers that offer researchers the ability to synthesize their own oligos. Researchers have the option to purchase BHQ dyes directly, either CPG-bound or as phosphoramidites or esters, to develop their own probes with BHQ technology “designed in,” or they can purchase BHQ probes developed by Biosearch Technologies based on the same groundbreaking dark quenching technology.


The original true dark quencher

The BHQ dyes are true dark quenchers with no native emission due to their polyaromatic-azo backbone. Substituting electron-donating and withdrawing groups on the aromatic rings produces a complete series of quenchers with broad absorption curves that span the visible spectrum.

BHQ dyes work through a combination of FRET and static quenching to enable researchers to avoid the residual background signal common to fluorescing quenchers such as TAMRA, or low signal to noise ratio.

These quenchers can be paired with all common reporter dyes to construct efficiently quenched qPCR probes for multiplexing assays. In addition to quenching by FRET, BHQ dyes have also been shown to efficiently quench fluorescence through static quenching via formation of a ground state complex with the reporter dye.

The difference between Black Hole Quencher (BHQ) dye and TAMRA

TAMRA dye is an effective quencher for fluorophores with emission maxima less than 560 nm. Dyes with longer wavelength emissions will not be effectively quenched by TAMRA. In addition, TAMRA has its own fluorescence which complicates data analysis due to crosstalk between the channels. In contrast, Black Hole Quencher™ dyes are true "dark" quenchers with no fluorescent signal. Their use simplifies design, implementation and interpretation of qPCR assays.

Furthermore, BHQ™ dyes have broad absorption spanning 480-580 nm (BHQ-1), 559-670 nm (BHQ-2) and 620-730 nm (BHQ-3), to enable use of a large range of spectrally distinct reporter dyes in multiplexed assay designs. With some dye pairings, FRET quenching is supplemented by the static quenching mechanism. Specifically, hydrophobic and electrostatic interactions facilitate the association of BHQ dyes with certain reporters to form an intramolecular dimer, for enhanced quenching and improved signal to noise ratios. Thus, BHQ dyes may quench some fluorophores whose emission spectrum is beyond the limits of BHQ absorption. 


Frequently Asked Questions

  1. What is a BHQ?

    Black Hole Quencher® (BHQ®) labels are a family of dark quenchers with excellent spectral overlap with all common reporter dyes for efficient FRET quenching. As a result, BHQ labels have become the industry standard for quenchers in dual-labeled hydrolysis probes and many other molecular probe formats.

  2. What is BHQ quencher?

    Black Hole Quencher™ dyes are true "dark" quenchers with no fluorescent signal, improving signal to noise ratios. Through a combination of FRET and static quenching, they deliver results without the residual background signal common to other quenchers. Their use simplifies design, implementation and interpretation of qPCR assays.

  3. What is a quencher in QPCR?

    A quencher is a type of molecule attached to an oligonucleotide that quenches fluorescence emitted by a fluorophore when excited by FRET (Förster Resonance Energy Transfer).

  4. How does a fluorescence quencher work?

    The reporter and quencher are placed at specific sites in an oligonucleotide such that a change in their distance will produce a maximal change in fluorescence and effectively signal the event being monitored (often hybridization or nuclease activity). The oligonucleotide acts as a flexible tether linking the fluorescent reporter and quencher.

  5. What is reporter and quencher?

    A reporter (such as FAM) and a quencher (such as BHQ-1 label) can bind together to form a new, nonfluorescent species called an intramolecular dimer. The biomolecule linking the reporter and quencher acts as a tether and enables intramolecular association between the reporter and quencher.

  6. What is quenching?

    Quenching is a mechanism used to absorb the fluorescence emitted by the reporter to produce a maximal change in fluorescence and effectively signal the event being monitored (often hybridization or nuclease activity)