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BHQ-2 Carboxylic Acid, Succinimidyl Ester

BHQ-2 Carboxylic Acid, Succinimidyl Ester

A carboxylic acid ester used for post-synthetic 5'-BHQ-2 labelling of oligonucleotides.

Key features

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  • Used to conjugate a non-fluorescent quencher to an amine functionality of a biomolecule.
  • Maximal absorption in the 560 to 670 nm range.
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Product information

Since their introduction to the DNA marketplace in 2000, the Black Hole Quenchers have become THE gold-standard quencher of choice used in qPCR probes and other FRET applications. When fluorogenic dual-labeled probes were first introduced, quenchers were often a second reporter dye, typically TAMRA. The sensitivity of these probes, such as FAM-TAMRA, is limited because the fluorescence from TAMRA can leak into the channel meant to detect FAM fluorescence. Dark quenchers, which are dyes with no native fluorescence, offer a solution to this problem. 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 into the near IR region. 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. BHQ quenchers have broad absorption spectra and can be paired with reporter dyes that emit in the following ranges: BHQ-0: 430-520 nm BHQ-1: 480-580 nm BHQ-2: 560-670 nm BHQ-3: 620-730 nm BHQ-10: 480-550 nm Water Soluble (WS) LGC, Biosearch Technologies offers all Black Hole Quencher products available for 3’, internal and 5’ modification of oligonucleotides with a variety of options. BHQ-1 and BHQ-2 are the more popular, either as the 5'-Phosphoramidites, the dT-Phosphoramidites or the 3'-CPGs. Only considering the excitation and emission values suggests Cy™5/Cyanine-5 and Quasar 670 require BHQ-3 for efficient quenching, however BHQ-2 is recommended because it is less susceptible to degradation. BHQ-1 is typically used to quench in the range 480 - 580 nm and can be used in conjunction with the commonly used fluorophores; e.g. FAM, TET, JOE and HEX. BHQ-2 is used to quench in the range 550 – 650 nm and is most effective in quenching fluorophores such as TAMRA, ROX, Cyanine-3, Cy3, Cy3.5™ and Red 640. We also offer Black Hole Quenchers for labelling peptides. All of our BHQ dyes are available as carboxylic acid or succinimidyl esters. Our BHQ-1 and BHQ-2 dyes are available as FMOC lysine conjugates. Our water soluble BHQ-10 is available as a carboxylic acid or succinimidyl ester.


  • Formula: C29H29N7O8
  • Molecular Weight: 603.6
  • Appearance: dark purple solid
  • Absorption Maximum (Lambda Max): 579
  • Extinction Coefficient at Lambda max: 38000
  • Extinction Coefficient at 260 nm: 8000

Product usage:

    The conjugation chemistry of the BHQ OSu may require 1 - 2 equiv. of a tertiary amine such as NMM or TEA which will deprotonate the target amine and not react with the OSu. The BHQ dye is stable in the presence of 95% TFA cleaving solution, however, BHQ-2 may be reduced by TFA treatment in the presence of 2% tri-isopropylsilane. Labeling peptides with dyes is an art that requires considerable trial and error even with experience, and each different peptide demands a unique optimization. For additional information you may review the reference publications, particularly the procedures listed in their Supplemental Information. Supplemental Information:Polster, B. M., Arze, R., Lyttle, M. H., Nicholls, D. G., & Hudson, D. (2007). “Solid Phase Synthesis of Dual Labeled Peptides: Development of Cell Permeable Calpain Specific Substrates. International Journal of Peptide Research and Therapeutics”, 13(1), 83-91.Lee, Seulki, et al. "Dark quenched matrix metalloproteinase fluorogenic probe for imaging osteoarthritis development in vivo." Bioconjugate chemistry 19.9 (2008): 1743-1747.Stefflova, K., Chen, J., Marotta, D., Li, H., & Zheng, G. (2006). “Photodynamic therapy agent with a built-in apoptosis sensor for evaluating its own therapeutic outcome in situ” Journal of medicinal chemistry, 49(13), 3850-3856.

Storage and handling:

  • Shipping conditions: Cold
  • Storage conditions: -15 to -30 °C

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