QXY21 NHS ester [equivalent to QSY-21 NHS ester]

QXY21 is the same molecule to QSY-21 acid (ThermoFisher). QSY-21 has a broad and intense absorption at ~661 nm maxima with no detectable fluorescence, making it useful as an acceptor in fluorescence resonance energy transfer (FRET) applications. It is a common long-wavelength quencher to best pair with Cy5, Alexa Fluor 647, iFluor 647 or other spectrally similar fluorescent dyes.

Calculators

Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of QXY21 NHS ester [equivalent to QSY-21 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 mg	0.5 mg	1 mg	5 mg	10 mg
1 mM	111.995 µL	559.973 µL	1.12 mL	5.6 mL	11.199 mL
5 mM	22.399 µL	111.995 µL	223.989 µL	1.12 mL	2.24 mL
10 mM	11.199 µL	55.997 µL	111.995 µL	559.973 µL	1.12 mL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)		Molecular weight		Volume (Calculate)		Concentration (Calculate)		Moles
	/		=		x		=

Spectrum

Open in Advanced Spectrum Viewer

Product family

Name	Excitation (nm)	Emission (nm)	Extinction coefficient (cm ^-1 M ^-1)	Quantum yield	Correction Factor (260 nm)	Correction Factor (280 nm)
Cy2DIGE NHS ester	492	508	150000	0.120	0.08	0.15
Cy3B NHS ester	560	571	120000¹	0.58¹	0.048	0.069
Cy3DIGE NHS ester	555	569	150000¹	0.15¹	0.07	0.073
Cy5DIGE NHS ester	651	670	250000¹	0.27¹, 0.4²	0.02	0.03
CypHer5E NHS Ester	643	660	-	-	-	-
CypHer7E NHS Ester	748	769	-	-	-	-
QXY7 NHS ester [equivalent to QSY-7 NHS ester]	-	-	90000¹	-	-	0.22
XFD350 NHS Ester	343	441	19000	-	0.25	0.19
XFD430 NHS ester	432	540	15,000	-	-	0.28
XFD488 NHS Ester	499	520	71000	0.92¹	0.30	0.11
XFD514 NHS Ester	518	543	80000	-	0.31	0.18
XFD532 NHS Ester	534	553	81000	0.61¹	0.24	0.09
XFD546 NHS Ester	561	572	112000	0.79¹	0.21	0.12
XFD555 NHS Ester	553	568	150000	0.1¹	0.08	0.08
XFD568 NHS Ester	579	603	91300	0.69¹	0.45	0.46
XFD594 NHS Ester	590	618	90000	0.66¹	0.43	0.56
XFD647 NHS Ester	650	671	239000	0.33¹	0.00	0.03
XFD660 NHS Ester	663	691	132000	-	0.00	0.10
XFD680 NHS Ester	681	704	184000	0.36¹	0.00	0.05
XFD700 NHS Ester	696	719	192000	0.25¹	0.00	0.07
XFD750 NHS Ester	752	776	240000	0.12¹	0.00	0.04
XFD790 NHS Ester	782	805	260,000	-	0.09	0.08
Show More (13)

Citations

View all 12 citations: Citation Explorer

A Sensitive Near-Infrared Fluorescent Sensor for Mitochondrial Hydrogen Sulfide
Authors: Ji, A., Fan, Y., Ren, W., Zhang, S., Ai, H. W.
Journal: ACS Sens (2018): 992-997

Imaging intracellular quantum dots: fluorescence microscopy and transmission electron microscopy
Authors: Szymanski, C. J., Yi, H., Liu, J. L., Wright, E. R., Payne, C. K.
Journal: Methods Mol Biol (2013): 21-33

Reversible off-on fluorescence probe for hypoxia and imaging of hypoxia-normoxia cycles in live cells
Authors: Takahashi, S., Piao, W., Matsumura, Y., Komatsu, T., Ueno, T., Terai, T., Kamachi, T., Kohno, M., Nagano, T., Hanaoka, K.
Journal: J Am Chem Soc (2012): 19588-91

Family of enhanced photoacoustic imaging agents for high-sensitivity and multiplexing studies in living mice
Authors: de la Zerda, A., Bodapati, S., Teed, R., May, S. Y., Tabakman, S. M., Liu, Z., Khuri-Yakub, B. T., Chen, X., Dai, H., Gambhir, S. S.
Journal: ACS Nano (2012): 4694-701

Visualizing mechanical tension across membrane receptors with a fluorescent sensor
Authors: Stabley, D. R., Jurchenko, C., Marshall, S. S., Salaita, K. S.
Journal: Nat Methods (2011): 64-7

References

View all 1 references: Citation Explorer

Synthesis and characterization of a small, membrane-permeant, caspase-activatable far-red fluorescent peptide for imaging apoptosis
Authors: Bullok K, Piwnica-Worms D.
Journal: J Med Chem (2005): 5404

Page updated on August 16, 2025

Ordering information

Price
Unit size
Catalog Number	2033
Quantity

Add to cart

Additional ordering information

Telephone	1-800-990-8053
Fax	1-800-609-2943
Email	sales@aatbio.com
International	See distributors
Bulk request	Inquire
Custom size	Inquire
Technical Support	Contact us
Purchase order	Send to sales@aatbio.com
Shipping	Standard overnight for United States, inquire for international

Request quotation

Physical properties

Molecular weight	892.90
Solvent	DMSO

Spectral properties

Absorbance (nm)	660
Correction Factor (280 nm)	0.32
Extinction coefficient (cm ^-1 M ^-1)	89000¹

Storage, safety and handling

H-phrase	H303, H313, H333
Hazard symbol	XN
Intended use	Research Use Only (RUO)
R-phrase	R20, R21, R22
Storage	Freeze (< -15 °C); Minimize light exposure
UNSPSC	12352200