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QXY7 NHS ester [equivalent to QSY-7 NHS ester]

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Physical properties
Molecular weight791.32
Spectral properties
Absorbance (nm)561
Correction Factor (280 nm)0.22
Extinction coefficient (cm -1 M -1)900001
Storage, safety and handling
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22
StorageFreeze (< -15 °C); Minimize light exposure


Molecular weight
Absorbance (nm)
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
QXY7 is the same molecule to QSY-7 acid (ThermoFisher). QXY7 has a broad and intense absorption at ~550 nm maxima with no detectable fluorescence, making it useful as an acceptor in fluorescence resonance energy transfer (FRET) applications paring with Cy3, TAMRA, Alexa Fluor 555 and iFluor 647 or other spectrally similar fluorescent dyes. QXY7 NHS ester is quite stable and readily reacts with amino-containing molecules such as amino-modified oligos, proteins and peptides.


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of QXY7 NHS ester [equivalent to QSY-7 NHS ester] to given concentration. Note that volume is only for preparing stock solution. Refer to sample experimental protocol for appropriate experimental/physiological buffers.

0.1 mg0.5 mg1 mg5 mg10 mg
1 mM126.371 µL631.856 µL1.264 mL6.319 mL12.637 mL
5 mM25.274 µL126.371 µL252.742 µL1.264 mL2.527 mL
10 mM12.637 µL63.186 µL126.371 µL631.856 µL1.264 mL

Molarity calculator

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Spectral properties

Absorbance (nm)561
Correction Factor (280 nm)0.22
Extinction coefficient (cm -1 M -1)900001

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)
XFD488 NHS Ester *Same Structure to Alexa Fluor™ 488 NHS Ester*499520710000.9210.300.11
XFD350 NHS Ester *Same Structure to Alexa Fluor™ 350 NHS Ester*34344119000-0.250.19
XFD532 NHS Ester *Same Structure to Alexa Fluor™ 532 NHS Ester*534553810000.6110.240.09
XFD594 NHS Ester *Same Structure to Alexa Fluor™ 594 NHS Ester*590618900000.6610.430.56
QXY21 NHS ester [equivalent to QSY-21 NHS ester]--890001--0.32
XFD555 NHS Ester *Same Structure to Alexa Fluor™ 555 NHS Ester*5535681500000.110.080.08
XFD647 NHS Ester *Same Structure to Alexa Fluor™ 647 NHS Ester*6506712390000.3310.000.03
XFD680 NHS Ester *Same Structure to Alexa Fluor™ 680 NHS Ester*6817041840000.3610.000.05
XFD700 NHS Ester *Same Structure to Alexa Fluor™ 700 NHS Ester*6967191920000.2510.000.07
XFD750 NHS Ester *Same Structure to Alexa Fluor™ 750 NHS Ester*7527762400000.1210.000.04
Cy5DIGE NHS ester65167025000010.271, 0.420.020.03
Cy2DIGE NHS ester4925081500000.1200.080.15
Cy3DIGE NHS ester55556915000010.1510.070.073
XFD546 NHS Ester *Same Structure to Alexa Fluor™ 546 NHS Ester*5615721120000.7910.210.12
XFD568 NHS Ester *Same Structure to Alexa Fluor™ 568 NHS Ester*579603913000.6910.450.46
XFD514 NHS Ester *Same Structure to Alexa Fluor™ 514 NHS Ester*51854380000-0.310.18
Cy3B NHS ester56057112000010.5810.0480.069
CypHer5E NHS Ester643660----
CypHer7E NHS Ester748769----
XFD660 NHS Ester [equivalent to Alexa Fluor® 660 NHS Ester]663691132000---
Show More (11)



View all 11 references: Citation Explorer
[Development of Novel Dark Quenchers and Their Application to Imaging Probes].
Authors: Hanaoka, Kenjiro
Journal: Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan (2019): 277-283
A real-time in vitro assay to evaluate the release of macromolecules from liposomes.
Authors: Mujoo, Himang and Reynolds, John N J and Tucker, Ian G
Journal: Drug testing and analysis (2018): 1025-1032
Structural exploration and Förster theory modeling for the interpretation of gas-phase FRET measurements: Chromophore-grafted amyloid-β peptides.
Authors: Kulesza, Alexander and Daly, Steven and MacAleese, Luke and Antoine, Rodolphe and Dugourd, Philippe
Journal: The Journal of chemical physics (2015): 025101
Action-FRET: probing the molecular conformation of mass-selected gas-phase peptides with Förster resonance energy transfer detected by acceptor-specific fragmentation.
Authors: Daly, Steven and Poussigue, Frédéric and Simon, Anne-Laure and MacAleese, Luke and Bertorelle, Franck and Chirot, Fabien and Antoine, Rodolphe and Dugourd, Philippe
Journal: Analytical chemistry (2014): 8798-804
Reversible off-on fluorescence probe for hypoxia and imaging of hypoxia-normoxia cycles in live cells.
Authors: Takahashi, Shodai and Piao, Wen and Matsumura, Yuriko and Komatsu, Toru and Ueno, Tasuku and Terai, Takuya and Kamachi, Toshiaki and Kohno, Masahiro and Nagano, Tetsuo and Hanaoka, Kenjiro
Journal: Journal of the American Chemical Society (2012): 19588-91
Tumor-specific detection of an optically targeted antibody combined with a quencher-conjugated neutravidin "quencher-chaser": a dual "quench and chase" strategy to improve target to nontarget ratios for molecular imaging of cancer.
Authors: Ogawa, Mikako and Kosaka, Nobuyuki and Choyke, Peter L and Kobayashi, Hisataka
Journal: Bioconjugate chemistry (2009): 147-54
A time-resolved, internally quenched fluorescence assay to characterize inhibition of hepatitis C virus nonstructural protein 3-4A protease at low enzyme concentrations.
Authors: Mao, Shi-Shan and DiMuzio, Jillian and McHale, Carolyn and Burlein, Christine and Olsen, David and Carroll, Steven S
Journal: Analytical biochemistry (2008): 1-8
Fluorescence-based sensing of glucose using engineered glucose/galactose-binding protein: a comparison of fluorescence resonance energy transfer and environmentally sensitive dye labelling strategies.
Authors: Khan, Faaizah and Gnudi, Luigi and Pickup, John C
Journal: Biochemical and biophysical research communications (2008): 102-6
Near-infrared fluorescent oligodeoxyribonucleotide reporters for sensing NF-kappaB DNA interactions in vitro.
Authors: Zhang, Surong and Metelev, Valeri and Tabatadze, David and Zamecnik, Paul and Bogdanov, Alexei
Journal: Oligonucleotides (2008): 235-43
Longer wavelength fluorescence resonance energy transfer depsipeptide substrates for hepatitis C virus NS3 protease.
Authors: Konstantinidis, Alex K and Richardson, Paul L and Kurtz, Kevin A and Tripathi, Rakesh and Chen, Chih-Ming and Huang, Peggy and Randolph, John and Towne, Danli and Donnelly, Jennifer and Warrior, Usha and Middleton, Tim and Kati, Warren M
Journal: Analytical biochemistry (2007): 156-67