AAT Bioquest

Cyanine 7 monosuccinimidyl ester [equivalent to Cy7® NHS ester]

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Physical properties
Molecular weight881.11
Spectral properties
Correction Factor (260 nm)0.05
Correction Factor (280 nm)0.036
Correction Factor (482 nm)0.0005
Correction Factor (565 nm)0.0193
Correction Factor (650 nm)0.165
Extinction coefficient (cm -1 M -1)250000
Excitation (nm)756
Emission (nm)779
Quantum yield0.3
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
Correction Factor (260 nm)
Correction Factor (280 nm)
Correction Factor (482 nm)
Correction Factor (565 nm)
Correction Factor (650 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Quantum yield
A variety of cyanine 7 (Cy7®) dyes has been used to label biological molecules for fluorescence imaging and other fluorescence-based biochemical analysis. They are widely used for labeling peptides, proteins and oligos etc. Cy7® dye conjugates are one type of the most common near infrared red fluorophores used in in vivo imaging applications. Cy7® NHS ester readily reacts with amino groups. AAT Bioquest offers Cy dye NHS esters in the form of triethylammonium salts that are more soluble in DMSO and DMF than the corresponding potassium salts that are offered by some other vendors. The Cy dye triethylammonium salts have the same reactivity and give the conjugates identical to the the Cy dye potassium salts. Cy7® is the trademark of GE Healthcare.

Example protocol


Unless otherwise noted, all unused stock solutions should be divided into single-use aliquots and stored at -20 °C after preparation. Avoid repeated freeze-thaw cycles.

1. Protein stock solution (Solution A)
Mix 100 µL of a reaction buffer (e.g., 1 M  sodium carbonate solution or 1 M phosphate buffer with pH ~9.0) with 900 µL of the target protein solution (e.g. antibody, protein concentration >2 mg/mL if possible) to give 1 mL protein labeling stock solution. Note: The pH of the protein solution (Solution A) should be 8.5 ± 0.5. If the pH of the protein solution is lower than 8.0, adjust the pH to the range of 8.0-9.0 using 1 M  sodium bicarbonate solution or 1 M pH 9.0 phosphate buffer. Note: The protein should be dissolved in 1X phosphate buffered saline (PBS), pH 7.2-7.4. If the protein is dissolved in Tris or glycine buffer, it must be dialyzed against 1X PBS, pH 7.2-7.4, to remove free amines or ammonium salts (such as ammonium sulfate and ammonium acetate) that are widely used for protein precipitation. Note: Impure antibodies or antibodies stabilized with bovine serum albumin (BSA) or gelatin will not be labeled well. The presence of sodium azide or thimerosal might also interfere with the conjugation reaction. Sodium azide or thimerosal can be removed by dialysis or spin column for optimal labeling results. Note: The conjugation efficiency is significantly reduced if the protein concentration is less than 2 mg/mL. For optimal labeling efficiency the final protein concentration range of 2-10 mg/mL is recommended.

2. Cyanine 7 monosuccinimidyl ester stock solution (Solution B)
Add anhydrous DMSO into the vial of Cyanine 7 monosuccinimidyl ester to make a 10 mM stock solution. Mix well by pipetting or vortex. Note: Prepare the dye stock solution (Solution B) before starting the conjugation. Use promptly. Extended storage of the dye stock solution may reduce the dye activity. Solution B can be stored in freezer for two weeks when kept from light and moisture. Avoid freeze-thaw cycles.


This labeling protocol was developed for the conjugate of Goat anti-mouse IgG with Cyanine 7 monosuccinimidyl ester. You might need further optimization for your particular proteins. Note: Each protein requires distinct dye/protein ratio, which also depends on the properties of dyes. Over labeling of a protein could detrimentally affects its binding affinity while the protein conjugates of low dye/protein ratio gives reduced sensitivity.

Run conjugation reaction
  1. Use 10:1 molar ratio of Solution B (dye)/Solution A (protein) as the starting point:  Add 5 µL of the dye stock solution (Solution B, assuming the dye stock solution is 10 mM) into the vial of the protein solution (95 µL of Solution A) with effective shaking. The concentration of the protein is ~0.05 mM assuming the protein concentration is 10 mg/mL and the molecular weight of the protein is ~200KD. Note: We recommend to use 10:1 molar ratio of Solution B (dye)/Solution A (protein). If it is too less or too high, determine the optimal dye/protein ratio at 5:1, 15:1 and 20:1 respectively.
  2. Continue to rotate or shake the reaction mixture at room temperature for 30-60 minutes. 

Purify the conjugation
The following protocol is an example of dye-protein conjugate purification by using a Sephadex G-25 column.
  1. Prepare Sephadex G-25 column according to the manufacture instruction.
  2. Load the reaction mixture (From "Run conjugation reaction") to the top of the Sephadex G-25 column.
  3. Add PBS (pH 7.2-7.4) as soon as the sample runs just below the top resin surface.
  4. Add more PBS (pH 7.2-7.4) to the desired sample to complete the column purification. Combine the fractions that contain the desired dye-protein conjugate. Note: For immediate use, the dye-protein conjugate need be diluted with staining buffer, and aliquoted for multiple uses. Note: For longer term storage, dye-protein conjugate solution need be concentrated or freeze dried. 


Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of Cyanine 7 monosuccinimidyl ester [equivalent to Cy7® 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 mM113.493 µL567.466 µL1.135 mL5.675 mL11.349 mL
5 mM22.699 µL113.493 µL226.986 µL1.135 mL2.27 mL
10 mM11.349 µL56.747 µL113.493 µL567.466 µL1.135 mL

Molarity calculator

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Spectral properties

Correction Factor (260 nm)0.05
Correction Factor (280 nm)0.036
Correction Factor (482 nm)0.0005
Correction Factor (565 nm)0.0193
Correction Factor (650 nm)0.165
Extinction coefficient (cm -1 M -1)250000
Excitation (nm)756
Emission (nm)779
Quantum yield0.3

Product Family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)Correction Factor (482 nm)Correction Factor (565 nm)
Cyanine 3 monosuccinimidyl ester [equivalent to Cy3® NHS ester]55556915000010.1510.070.073--
Cyanine 5 monosuccinimidyl ester [equivalent to Cy5® NHS ester]65167025000010.271, 0.420.020.030.0090.09
Cyanine 7 bissuccinimidyl ester [equivalent to Cy7® bisNHS ester]7567792500000.30.050.0360.00050.0193



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View all 21 references: Citation Explorer
Excitation of Cy5 in self-assembled lipid bilayers using optical microresonators
Authors: Freeman LM, Li S, Dayani Y, Choi HS, Malmstadt N, Armani AM.
Journal: Appl Phys Lett (2011): 143703
Theranostic cRGD-BioShuttle Constructs Containing Temozolomide- and Cy7 For NIR-Imaging and Therapy
Authors: Wiessler M, Hennrich U, Pipkorn R, Waldeck W, Cao L, Peter J, Ehemann V, Semmler W, Lammers T, Braun K.
Journal: Theranostics (2011): 381
Rational approach to select small peptide molecular probes labeled with fluorescent cyanine dyes for in vivo optical imaging
Authors: Berezin MY, Guo K, Akers W, Livingston J, Solomon M, Lee H, Liang K, Agee A, Achilefu S.
Journal: Biochemistry (2011): 2691
In vivo detection of embryonic stem cell-derived cardiovascular progenitor cells using Cy3-labeled Gadofluorine M in murine myocardium
Authors: Adler ED, Bystrup A, Briley-Saebo KC, Mani V, Young W, Giovanonne S, Altman P, Kattman SJ, Frank JA, Weinmann HJ, Keller GM, Fayad ZA.
Journal: JACC Cardiovasc Imaging (2009): 1114
Quantitative proteomics by fluorescent labeling of cysteine residues using a set of two cyanine-based or three rhodamine-based dyes
Authors: Volke D, Hoffmann R.
Journal: Electrophoresis (2008): 4516
Surface plasmon resonance-enhanced fluorescence implementation of a single-step competition assay: demonstration of fatty acid measurement using an anti-fatty acid monoclonal antibody and a Cy5-labeled fatty acid
Authors: Vareiro MM, Tranchant I, Maplin S, Zak K, Gani MM, Slevin CJ, Hailes HC, Tabor AB, Cameron PJ, Jenkins AT, Williams DE.
Journal: Anal Biochem (2008): 243
Thiazole orange and Cy3: improvement of fluorescent DNA probes with use of short range electron transfer
Authors: Menacher F, Rubner M, Berndl S, Wagenknecht HA.
Journal: J Org Chem (2008): 4263
Near-infrared fluorescence imaging of tumor integrin alpha v beta 3 expression with Cy7-labeled RGD multimers
Authors: Wu Y, Cai W, Chen X.
Journal: Mol Imaging Biol (2006): 226
Carbobenzoxy-capped Phe-Lys(Cy5)-acyloxymethyl ketone
Authors: Shan L., undefined
Journal: In: Molecular Imaging and Contrast Agent Database (MICAD), Bethesda (MD). (2004)
Cys-Arg-Glu-Lys-Ala-superparamagnetic iron oxide-Cy7 nanoparticles
Authors: Leung K., undefined
Journal: In: Molecular Imaging and Contrast Agent Database (MICAD), Bethesda (MD). (2004)