Labeling Reagents


QXL® - Efficient  proprietary Quenchers

Quenchers are frequently used in tandem with fluorescent dyes to generate FRET pairs. The most classical FRET pairs are Mca/Dnp and EDANS/DABCYL, both emitting in the blue channel.

Their short absorption wavelength and low extinction coefficient limit their use as several proteomic samples show background autofluorescence in the blue wavelengths.

Due to the high interest in developing FRET pairs with longer emission wavelengths, AnaSpec (Eurogentec's US subsidiary) has developed the QXL® range of dark quenchers. They are individually optimized to pair with all popular fluorescent dyes such as fluoresceins and rhodamines as well as our superior HiLyte™ fluor dyes.

Our line of QXL® cover the full visible spectrum with unusually high efficiency.

Our dye/quencher labeling offer

We offer a full-range of dye-quencher FRET pairs and fluorogenic substrates.
The tables below list the dyes and quenchers available to label your custom peptides

FRET Pairs
Dye (donor) Quencher (acceptor) Donor Ex/Em
Mca Dnp

 325/393 nm


 335/493 nm


 492/518 nm


 494/519 nm

HiLyte™ Fluor 488 QXL®520

 502/527 nm

CyLyte Fluor 3 QXL®570

 550/564 nm

HiLyte™ Fluor 532 QXL®570

 545/565 nm

HiLyte™ Fluor 555 QXL®570

 550/566 nm


 541/568 nm

Rox QXL®610

 568/591 nm

CyLyte Fluor 5 QXL®670

 648/663 nm

HiLyte™ Fluor 647 QXL®670

 650/675 nm

CyLyte Fluor 7 IR-QXL®

 750/773 nm

QXL®490, 570, 670 are available as stand-alone catalog products, while our most popular QXL®520 and QXL®610 are exclusively available via our custom labeling services.

  • Fluorescent Dyes

    Standard and proprietary efficient dyes

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  • FRET Peptides

    We propose a full range of dye-quencher pairs for customized assay development

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