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Cy3 maleimide (non-sulfonated)
Labeling of cysteine residues, as well as other thiolated molecules

Catalog No.A8138
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Sample solution is provided at 25 µL, 10mM.

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Chemical structure

Cy3 maleimide (non-sulfonated)

Related Biological Data

Cy3 maleimide (non-sulfonated)

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Chemical Properties

Cas No. N/A SDF Download SDF
Synonyms N/A
Chemical Name 1-(6-((2-(2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl)ethyl)amino)-6-oxohexyl)-3,3-dimethyl-2-((1E,3E)-3-(1,3,3-trimethylindolin-2-ylidene)prop-1-en-1-yl)-3H-indol-1-ium
Canonical SMILES CC1(C)C2=CC=CC=C2[N+](CCCCCC(NCCN3C(C=CC3=O)=O)=O)=C1/C=C/C=C4C(C)(C)C5=CC=CC=C5N\4C
Formula C36H43ClN4O3 M.Wt 615.20
Solubility soluble in organic solvents (DMF, DMSO, dichloromethane), insoluble in water Storage 24 months after receival at -20°C in the dark. Transportation: at room temperature for up to 3 weeks. Avoid prolonged exposure to light. Desiccate
Shipping Condition Evaluation sample solution : ship with blue ice.All other available size: ship with RT , or blue ice upon request
General tips For obtaining a higher solubility , please warm the tube at 37 ℃ and shake it in the ultrasonic bath for a while.Stock solution can be stored below -20℃ for several months.

Spectral properties

Excitation max (nm) 555 Emission max (nm) 570
Extinction Coefficient (M-1cm-1) 150000 Quantum Yield 0.31
CF260 0.04 CF280 0.09


Non-sulfonated cyanines are available for the labeling of many targets including:

• Soluble proteins, which are tolerant to addition of organic co-solvent • Fluorescence polarization (FP)
• Antibodies (with 5-10% of DMSO/DMF) • Fluorescence resonance energy transfer (FRET)
• DNA and oligonucleotides • Time-resolved fluorescence energy transfer (TR-FRET)
• Peptides • Fluorescence intensity (FI)
• Many small molecules  
• Reactions in organic media (dichloromethane, acetonitrile)  


Cy3 maleimide is a selective and efficient fluorophore dye with low aqueous solubility. This labeling reagent can be used to attach Cy3 fluorophore to proteins and peptides which contain cysteine residues, as well as to other thiolate molecules (such as thiol-containing oligonucleotides). Before the labeling reactions, Cystines should be reduced with TCEP (tris-carboxyethylphosphine). For biomolecule labeling, the labeling reagent has low aqueous solubility, using of organic co-solvent to dissolve this molecular is necessary for efficient reaction. First, Cyanine dye should be dissolved in organic solvent and then added to a solution of biomolecule in appropriate aqueous buffer.

MSNs were labeled by Cy3 maleimide named MSN-Cy3s at the concentration of 10 μg ml-1. MSN-Cy3s incubated with MEF-mEGFP cells on a glass coverslip in culture medium for 2 h To further visualize the MSN locations in the cytosol we used super-resolution microscopy (3D SIM). The visually microscope image results confirm that MSNs were internalized by MEF-mEGFP cells [1].

[1].  Chiu, H.-Y.; Deng, W.; Engelke, H.; Helma, J.; Leonhardt, H.; Bein, T. Intracellular chromobody delivery by mesoporous silica nanoparticles for antigen targeting and visualization in real time. Scientific Reports, 2016, 6, 25019.