QSY 21 NHS 

QSY 21 NHS is a dark quencher and an efficient energy transfer acceptor for far-red and near-infrared fluorescent probes. QSY 21 NHS operates at a wavelength range of 540-750 nm and is commonly used in FRET applications. QSY 21 NHS does not fluoresce under normal conditions. The NHS ester can be used to label primary amines (R-NH₂) of proteins, amine-modified oligonucleotides and other amine-containing molecules. QSY 21 NHS can be conjugated with dendritic poly-L-lysine to achieve intramolecular quenching of Cy5 fluorescence^[1][2].

QSY21-NHS (1:7 Cy5:QSY21 molar ratio; 1 h (serum/GSH); 2 h (caspase-3 assay)) achieves complete FRET quenching of Cy5, maintains stability in serum and GSH, and enables caspase-3-dependent fluorescence activation via cleavage of the DEVD linker^[2].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

QSY 21 NHS (Conjugated to DGLs at a Cy5:QSY 21 molar ratio of 1:7 as part of 600 μg/rat brain-targeted nano-device; tail vein; single dose), as part of the brain-targeted DGLs-RVG29-FRET nano-device, enables in vivo detection of activated caspase-3 in rotenone-induced Parkinson's disease model rats, with peak fluorescence signal intensity (2.5-fold higher than untreated rats) observed after 10 days of rotenone treatment^[2].
QSY 21 NHS (Conjugated to DGLs at a Cy5:QSY 21 molar ratio of 1:7 as part of brain-targeted nano-device; intravenous), as part of the RVG29-modified brain-targeted nano-device, exhibits enhanced accumulation in the brains of healthy mice, with peak brain signal observed 1 hour after intravenous administration^[2].

MedChemExpress (MCE) has not independently confirmed the accuracy of these methods. They are for reference only.

815.33

C₄₅H₃₉ClN₄O₇S

304014-13-9

Solid

Purple to purplish red

O=C(C1CCN(S(=O)(C2=C(C3=C4C=CC(N5C6=C(CC5)C=CC=C6)=CC4=[O+]C7=C3C=CC(N8C9=C(CC8)C=CC=C9)=C7)C=CC=C2)=O)CC1)ON%10C(CCC%10=O)=O.[Cl-]

Room temperature in continental US; may vary elsewhere.

-20°C, sealed storage, away from moisture and light

*In solvent : -80°C, 6 months; -20°C, 1 month (sealed storage, away from moisture and light)

* Please refer to the solubility information to select the appropriate solvent. Once prepared, please aliquot and store the solution to prevent product inactivation from repeated freeze-thaw cycles.
Storage method and period of stock solution: -80°C, 6 months; -20°C, 1 month (sealed storage, away from moisture and light). When stored at -80°C, please use it within 6 months. When stored at -20°C, please use it within 1 month.

• [1]. Ben-Nun Y, et al. Photodynamic quenched cathepsin activity based probes for cancer detection and macrophage targeted therapy. Theranostics. 2015;5(8):847-862. Published 2015 Apr 27.

  [2]. Liu Y, et al. Targeted imaging of activated caspase-3 in the central nervous system by a dual functional nano-device. J Control Release. 2012;163(2):203-210.