DusQ

DusQ 1 amidite, 5'-terminal

CAT: A20-0014

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DusQ 1 CPG 1000

CAT: A20-0015

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DusQ 1 dT phosphoramidite

CAT: A20-0016

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DusQ 1 NHS ester

CAT: A20-0017

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DusQ 1 phosphoramidite

CAS No.:374591-94-3

Purity:≥95%

CAT: A20-0018

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DusQ 21 carboxylic acid

CAS No.:1200894-41-2

CAT: A20-0019

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DusQ 21 CPG 500

CAT: A20-0020

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DusQ 21 NHS ester

CAS No.:304014-13-9

CAT: A20-0021

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DusQ 2 CPG 1000

CAT: A20-0022

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DusQ 2 CPG 500

CAT: A20-0023

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DusQ 2 dT phosphoramidite

CAT: A20-0024

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DusQ 2 NHS ester

CAT: A20-0025

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DusQ 3 azide

CAT: A20-0026

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DusQ 3 CPG 500

CAT: A20-0027

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DusQ 3 NHS ester

CAT: A20-0028

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Background

DusQ quencher is a series of highly efficient non-fluorescent quenchers, widely used in fluorescence resonance energy transfer (FRET) probes, real-time quantitative PCR (qPCR), and molecular hybridization techniques. These quenchers effectively reduce background signals and enhance detection sensitivity by absorbing the energy emitted by fluorescent dyes without emitting fluorescence themselves. At BOC Sciences, the diverse DusQ quencher product line offers researchers a highly flexible range of probe design options, which can be matched according to the dye combination, wavelength requirements, sample type, and detection platform of each experiment, maximizing quenching efficiency and signal-to-noise ratio. By precisely selecting the appropriate type of DusQ, scientists can construct highly specific, low-background, and rapidly responsive fluorescent probe systems, effectively supporting a variety of applications from basic research to molecular diagnostics.

What is DusQ Quencher?

In modern molecular biology experiments, fluorescence probe technology is widely used in key areas such as nucleic acid detection, protein-protein interaction analysis, live-cell imaging, and real-time quantitative PCR. One of the core mechanisms of fluorescence probes is fluorescence quenching, in which the light emitted by fluorescent dyes is effectively suppressed by a quencher, enabling signal release and detection under specific conditions. The DusQ quencher series is designed precisely for this purpose as a class of efficient dark quenchers. Their most prominent feature is that they do not produce their own fluorescence but instead absorb the energy emitted by fluorescent dyes and convert it into heat energy.

What is the Principle of DusQ Quencher?

The working principle of DusQ quencher is based on the FRET mechanism. When the distance between a fluorescent donor (fluorophore) and the quencher acceptor is sufficiently close (typically less than 10 nm), the energy released from the excited state of the donor can be transferred directly to the acceptor molecule via a non-radiative process, thereby suppressing the fluorescence emission of the donor. Due to its broad absorption spectrum, DusQ quencher can be paired with various fluorescent dyes, making it an ideal energy acceptor.

Compared with traditional fluorescent quenchers (such as TAMRA, which are themselves fluorescent), DusQ quencher belongs to the category of non-emissive quenchers. It does not possess inherent fluorescence, avoiding background signal generation in detection systems. Therefore, it is particularly advantageous in high-sensitivity detection methods such as multiplex qPCR or FRET imaging experiments. This silent property significantly improves the signal-to-noise ratio, especially in cases involving low-copy targets or trace samples, ensuring clear and reliable signal changes. Moreover, DusQ quencher structures are optimized to covalently couple with biomolecules such as oligonucleotides, proteins, or peptides, enabling precise spatial positioning and maximizing energy transfer efficiency. Through this precise design, the fluorescent dye and quencher remain in an "off" state until a biological reaction (e.g., enzymatic cleavage, conformational change, hybridization) occurs, causing a change in distance or dissociation, which deactivates the quenching and releases the fluorescent signal—thus forming a switch-type fluorescence response system.

Main Types of DusQ Quenchers

Different types of DusQ possess specific absorption spectral ranges and can be matched with various fluorescent dyes to meet different application requirements in single or multiplex detection. Based on their absorption wavelengths and structural characteristics, the commonly used DusQ Quenchers currently include DusQ 1, DusQ 2, DusQ 21, and DusQ 3, each optimized for the emission wavelength range of different fluorescent dyes. Below are detailed descriptions of the main types:

• DusQ 1: Ideal Quencher for Green-Yellow Channel

DusQ 1 is one of the earliest and most widely used types in the series, with a maximum absorption wavelength of approximately 534 nm and a coverage range of 480–580 nm. It is particularly suitable for use with fluorescent dyes emitting in the green to yellow region, such as FAM, TET, HEX, and JOE. It is a common choice for real-time qPCR and molecular hybridization probes (e.g., TaqMan, Molecular Beacon). Its high quenching efficiency and excellent thermal stability enable it to maintain function even during high-temperature PCR reactions, making it suitable for long-term use and high-throughput detection. DusQ 1 is typically introduced at the 3' or 5' end of the oligonucleotide strand in the form of phosphoramidite or CPG, allowing precise labeling during chemical synthesis.

• DusQ 2: Efficient Quencher for Red-Orange Region

DusQ 2 extends its absorption range to 560–670 nm, suitable for quenching dyes with emission spectra in the red-orange region, such as TAMRA, ROX, Cyanine3, and Alexa Fluor 555. This type has a broader absorption coverage, enabling effective use in multiplex fluorescence detection, maximizing background signal reduction while ensuring clear dye fluorescence. In addition, DusQ 2 is also commonly used as a dark quencher in FRET studies involving protein or peptide probe designs, showing excellent performance in structural variation detection and bioenzyme activity analysis. Due to its non-fluorescent nature, it does not introduce additional background interference, even in complex biological systems, making it especially suitable for analyzing cell samples with inherently high background.

• DusQ 21: Advanced Quencher for Far-Red and Near-Infrared Region

To meet the demands of high-wavelength fluorescent dyes, DusQ 21 was developed. This type has a maximum absorption wavelength of approximately 656 nm and covers the range suitable for dyes such as Cyanine5, AF647, Alexa Fluor 660, and Atto 655, which emit in the far-red and near-infrared regions. Compared with traditional quenchers, DusQ 21 has a more complex structure but higher quenching efficiency, making it suitable for applications such as deep tissue imaging, high-sensitivity nucleic acid detection, and multiplex target analysis. Its excellent photostability and quenching ability have led to expanded use in high-end diagnostic kits and complex systems. It is also well-suited for developing systems that combine real-time detection and imaging.

• DusQ 3: Specifically Designed for Near-Infrared Dye Pairing

DusQ 3 is one of the types in the DusQ series with the broadest absorption wavelength range and one of the closest to the near-infrared region. It is suitable for pairing with dyes such as Cyanine5.5, IRDye 700, and DyLight 680. With a maximum absorption wavelength approaching 670–700 nm, it is ideal for achieving efficient signal control in low-background near-infrared channels. DusQ 3 is particularly advantageous in the analysis of complex biological samples, such as blood and tissue extracts. In high-throughput FRET applications, disease biomarker detection, and small animal in vivo imaging, its non-intrinsic fluorescence can significantly improve detection sensitivity and specificity.

Type Comparison and Selection Recommendations

Synthesis and Modification of DusQ Quencher

The outstanding performance of DusQ quencher stems not only from its unique molecular structure design but also from its sophisticated chemical synthesis route and diversified structural modification strategies. As a class of dark quenchers (non-fluorescent quenchers), the synthesis of DusQ takes into account various requirements such as absorption efficiency, spectral range, chemical stability, and biocompatibility.

• Synthesis Principles and Scaffold Design of DusQ

DusQ quenchers generally use highly conjugated non-luminescent dyes as the backbone, with common core structures including carbazole, thiophene, anthraquinone, and phenothiazine. These structures exhibit strong light absorption abilities without visible fluorescence emission. The introduction of substituents (e.g., nitro, carboxyl, sulfonic acid groups) can further modulate their electronic properties and solubility. The key design principle of DusQ is to maximize quenching efficiency while minimizing intrinsic fluorescence. Its molecules typically incorporate multiple conjugated aromatic rings and electron-rich structural units, enabling broad-spectrum absorption that spans from green fluorescence (e.g., FAM) to near-infrared regions (e.g., Cy5, Cy7), thereby achieving universal quenching.

• Functional Modifications and Introduction of Reactive Groups

To enable covalent coupling with target molecules, DusQ quenchers are usually modified with reactive functional groups, such as:

• NHS Ester (N-hydroxysuccinimide ester): Reacts efficiently with primary amines or lysine side chains to form amide bonds, widely used in protein labeling.
• Maleimide: Selectively reacts with thiol groups (-SH), suitable for biomolecules like peptides and antibody fragments containing cysteine.
• Azide and Alkyne Groups: Applied in click chemistry reactions (e.g., CuAAC), extensively used for nucleic acid and polymer probe modifications.
• Carboxyl (-COOH) and Amino (-NH₂) Groups: Serve as basic functional groups for subsequent modifications or conjugation.

These functional groups are typically introduced at later stages of synthesis to preserve the stability of the core dye structure. Some DusQ products also employ PEG spacers (e.g., PEG₄, PEG₁₂) for spatial adjustment, enhancing flexibility and water solubility in macromolecular labeling.

• Construction Strategies for DusQ Fluorescent Conjugated Probes

DusQ is typically used as the 3'- or 5'-terminal labeling component in probes, forming a fluorescence-quenching system (FRET pair) with fluorescent dyes. Main construction methods include:

• Incorporation During Solid-Phase Synthesis: During oligonucleotide synthesis, phosphoramidite compounds modified with DusQ can be directly inserted at the end of the oligomer chain, ensuring labeling accuracy and high reaction efficiency.
• Solution-Phase Conjugation: For protein, antibody, or enzyme labeling, covalent coupling is conducted in solution using active esters or maleimide groups. Reaction conditions (e.g., pH, temperature) must be controlled to avoid side reactions.
• Click Chemistry Conjugation: Efficient labeling under mild conditions via 1,3-dipolar cycloaddition between azide and alkyne groups, particularly suitable for biomolecules sensitive to heat or acid.

Additionally, bifunctional probe construction techniques can incorporate both fluorescent dyes and DusQ into a single probe, forming an emission-quenching pair for dynamic signal control.

• Optimization of DusQ Quenching Efficiency and Structural Adjustments

To maximize FRET efficiency, DusQ molecules must exhibit strong spectral overlap characteristics and spatial responsiveness. Studies show that adjusting the following parameters can further optimize performance:

• Extension of Conjugated Structures: Introducing larger conjugated systems enhances absorption wavelengths and broadens the absorption band, supporting quenching of far-red dyes.
• Steric Structural Modulation: Using flexible or rigid linkers (e.g., alkyl chains, PEG, aromatic rings) to control the spatial distance between fluorescent donors and quenchers improves system responsiveness.
• Dual Quenching Design: Incorporating two DusQ molecules at both ends of a probe enhances bidirectional quenching upon probe folding, improving background suppression—especially suitable for molecular beacon systems.

Applications of DusQ Quenchers

With the rapid advancement of fluorescent probe technologies in biomedicine, molecular diagnostics, environmental monitoring, and drug screening, the demand for high-efficiency, low-background quenchers continues to rise. As a new-generation non-radiative dark quencher, DusQ demonstrates unique advantages in various cutting-edge applications due to its excellent optical properties and broad dye compatibility.

• Real-Time Quantitative PCR (qPCR) and Molecular Diagnostics

DusQ plays a crucial role in qPCR, particularly in TaqMan probes and molecular beacon systems. Traditional quenchers like DABCYL or TAMRA often emit weak fluorescence, leading to background signal interference. In contrast, DusQ significantly improves signal-to-noise ratio through its non-fluorescent nature, ensuring low background and high-sensitivity fluorescence output. This feature holds great value in clinical molecular diagnostics such as cancer mutation detection, rapid pathogen nucleic acid testing (e.g., SARS-CoV-2, HPV, HBV), and is especially advantageous in multiplex qPCR. Various DusQ types can be paired with multicolor dyes to enable simultaneous detection of multiple targets.

• Nucleic Acid Hybridization Probes and Molecular Imaging

In nucleic acid detection techniques such as fluorescence in situ hybridization (FISH) and SmartFlare probes, the quencher's performance directly affects visualization and hybridization accuracy. DusQ, with its non-luminescent property and excellent thermal stability, maintains quenching ability during high-temperature hybridization, suitable for spatial localization of targets like mRNA, miRNA, and lncRNA. Moreover, in live-cell or in vivo systems—such as FRET-based nucleic acid probes—DusQ forms signal-switch probes with fluorescent dyes, releasing fluorescence only under specific conditions to dynamically monitor molecular events (e.g., RNA expression, enzyme activity changes).

• Protein Interaction and Enzyme Activity Analysis

DusQ is widely used in studying protein–protein and protein–nucleic acid interactions. In a FRET system, the fluorescent donor is labeled on one molecule (e.g., a protein or ligand) and DusQ on the interacting partner, forming a distance-dependent quenching system. Fluorescence is quenched when in proximity and restored upon dissociation. This mechanism is valuable for enzyme inhibitor screening, protein conformational studies, and protein complex formation analysis, particularly in high-throughput screening platforms. The structural stability and chemical compatibility of DusQ also facilitate its conjugation to peptides, antibodies, and enzymes, expanding its use in biochemistry and pharmacology.

• Live-Cell and Small Animal Imaging

Background fluorescence is a critical issue in live-cell or small animal fluorescence imaging, especially in complex samples like tissues or blood. DusQ's non-emissive quenching mechanism minimizes background excitation, improving signal detection accuracy. For instance, nucleic acid probes labeled with DusQ emit fluorescence only upon binding to target RNA, allowing clearer intracellular signal visualization. In small animal models (e.g., for cancer or neurological disease RNA tracking), high-wavelength DusQ types such as DusQ 21 and DusQ 3 can be paired with near-infrared dyes (e.g., Cy5.5, AF680) to provide deep tissue penetration and low-background imaging advantages.

• Environmental Biosensors and Nanotechnology Platforms

DusQ is extensively applied in nanometal probe systems (e.g., gold nanoparticles, quantum dots) for detecting heavy metal ions, pollutants, and harmful microorganisms. For example, DusQ at the 3' end of nucleic acid aptamer probes can form efficient FRET systems with gold nanoparticles, emitting fluorescence only in the presence of specific contaminants, enabling rapid and highly specific switch-type detection. Additionally, DusQ plays a key role in fluorescent modulation elements for constructing DNA origami and molecular logic gates, offering potential for future intelligent sensing and responsive material innovations.

• Clinical In Vitro Diagnostics (IVD) Product Development

DusQ is increasingly used in IVD products, such as fluorescent PCR kits and rapid nucleic acid test strips. Its stable quenching performance and low fluorescence background significantly enhance sensitivity and reliability. For instance, in portable molecular detection platforms such as microfluidic fluorescence analyzers or CRISPR-detection systems, DusQ provides strong signal differentiation capabilities, serving as a key component in rapid diagnostics (e.g., infectious disease screening, cancer screening, personalized medicine).

Conclusion

The DusQ quencher series, as highly efficient non-fluorescent quenchers, have become indispensable tools in molecular biology research due to their broad absorption range, strong quenching efficiency, and versatile modification options. Whether in real-time PCR, molecular hybridization probe design, or FRET applications, DusQ quenchers demonstrate outstanding performance, enabling researchers to achieve higher sensitivity and specificity in detection. With the ongoing integration of fluorescence technology, nanotechnology, and bioinformatics, their application prospects continue to expand, and they are expected to play an increasingly pivotal role in emerging fields such as precision medicine, intelligent diagnostics, and synthetic biology.