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

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.

QSY-21 NHS esters (or succinimidyl esters) readily reacts with the primary amines (R-NH<sub>2</sub>) of proteins, amine-modified oligonucleotides, and other amine-containing molecules. The resulting dye conjugates are quite stable.

Protocol

SDS

COA

Catalog	Size	Price	Quantity
2033	10 mg	Price

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
mg	÷	892.9 g/mol	=	mL	x	mM	=	mmol

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

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)	89000 ¹

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

Documents

Protocol
Safety Data Sheet
Certificate of Analysis

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Page updated on October 25, 2025