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Cyanine 3 maleimide [equivalent to Cy3® maleimide]
A variety of cyanine 3 (Cy3®) 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. Cy3® dyes have enhanced fluorescence upon binding to proteins. Cy3® maleimide readily reacts with thiol groups. Cy3® is the trademark of GE Healthcare.
Example protocol
PREPARATION OF STOCK SOLUTIONS
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. Cyanine 3 maleimide stock solution (Solution B)
Add anhydrous DMSO into the vial of Cyanine 3 maleimide 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 upto 4 weeks when kept from light and moisture. Avoid freeze-thaw cycles.2. Protein stock solution (Solution A)
Mix 100 µL of a reaction buffer (e.g., 100 mM MES buffer with pH ~6.0) 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 6.5 ± 0.5. Note: Impure antibodies or antibodies stabilized with bovine serum albumin (BSA) or other proteins will not be labeled well. 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.3. Optional
if your protein does not contain a free cysteine, you must treat your protein with DTT or TCEP to generate a thiol group. DTT or TCEP are used for converting a disulfide bond to two free thiol groups. If DTT is used you must remove free DTT by dialysis or gel filtration before conjugating a dye maleimide to your protein. Following is a sample protocol for generating a free thiol group:- Prepare a fresh solution of 1 M DTT (15.4 mg/100 µL) in distilled water.
- Make IgG solution in 20 mM DTT: add 20 µL of DTT stock per ml of IgG solution while mixing. Let stand at room temp for 30 minutes without additional mixing (to minimize reoxidation of cysteines to cystines).
- Pass the reduced IgG over a filtration column pre-equilibrated with "Exchange Buffer". Collect 0.25 mL fractions off the column.
- Determine the protein concentrations and pool the fractions with the majority of the IgG. This can be done either spectrophotometrically or colorimetrically.
- Carry out the conjugation as soon as possible after this step (see Sample Experiment Protocol). Note: IgG solutions should be >4 mg/mL for the best results. The antibody should be concentrated if less than 2 mg/mL. Include an extra 10% for losses on the buffer exchange column. Note: The reduction can be carried out in almost any buffers from pH 7-7.5, e.g., MES, phosphate or TRIS buffers. Note: Steps 3 and 4 can be replaced by dialysis.
SAMPLE EXPERIMENTAL PROTOCOL
This labeling protocol was developed for the conjugate of Goat anti-mouse IgG with Cyanine 3 maleimide. 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
- 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.
- 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.- Prepare Sephadex G-25 column according to the manufacture instruction.
- Load the reaction mixture (From "Run conjugation reaction") to the top of the Sephadex G-25 column.
- Add PBS (pH 7.2-7.4) as soon as the sample runs just below the top resin surface.
- 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.
Calculators
Common stock solution preparation
Table 1. Volume of DMSO needed to reconstitute specific mass of Cyanine 3 maleimide [equivalent to Cy3® maleimide] 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 | 115.351 µL | 576.754 µL | 1.154 mL | 5.768 mL | 11.535 mL |
| 5 mM | 23.07 µL | 115.351 µL | 230.702 µL | 1.154 mL | 2.307 mL |
| 10 mM | 11.535 µL | 57.675 µL | 115.351 µL | 576.754 µL | 1.154 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
Product family
| Name | Excitation (nm) | Emission (nm) | Extinction coefficient (cm -1 M -1) | Quantum yield | Correction Factor (260 nm) | Correction Factor (280 nm) |
| Cyanine 3 bisacid [equivalent to Cy3® bisacid] | 555 | 569 | 1500001 | 0.151 | 0.07 | 0.073 |
| Cyanine 3 monoacid [equivalent to Cy3® acid] | 555 | 569 | 1500001 | 0.151 | 0.07 | 0.073 |
| Cyanine 5 maleimide [equivalent to Cy5® maleimide] | 651 | 670 | 2500001 | 0.271, 0.42 | 0.02 | 0.03 |
| Cyanine 7 maleimide [equivalent to Cy7® maleimide] | 756 | 779 | 250000 | 0.3 | 0.05 | 0.036 |
| Cyanine-3- dUTP [Cy3-dUTP] *1 mM in TE Buffer (pH 7.5)* | 555 | 569 | 1500001 | 0.151 | 0.07 | 0.073 |
Citations
View all 18 citations: Citation Explorer
ATP promotes protein coacervation through conformational compaction
Authors: Zhu, Yueling and Lin, Shiyan and Meng, Lingshen and Sun, Min and Liu, Maili and Li, Jingyuan and Tang, Chun and Gong, Zhou
Journal: Journal of Molecular Cell Biology (2024): mjae038
Authors: Zhu, Yueling and Lin, Shiyan and Meng, Lingshen and Sun, Min and Liu, Maili and Li, Jingyuan and Tang, Chun and Gong, Zhou
Journal: Journal of Molecular Cell Biology (2024): mjae038
Competitive binding-mediated mesoscale protein-protein interactions direct microtubule growth
Authors: Wei, Zhiyi and Jia, Xuanyan and Lin, Leishu and Guo, Siqi and Zhou, Lulu and Jin, Gaowei and Dong, Jiayuan and Xiao, Jinman and Xie, Xingqiao and Li, Yiming and others,
Journal: (2024)
Authors: Wei, Zhiyi and Jia, Xuanyan and Lin, Leishu and Guo, Siqi and Zhou, Lulu and Jin, Gaowei and Dong, Jiayuan and Xiao, Jinman and Xie, Xingqiao and Li, Yiming and others,
Journal: (2024)
Conformational compaction as a mechanism for ATP resolubilization of protein condensates
Authors: Gong, Zhou and Zhu, Yueling and Lin, Shiyan and Meng, Ling-Shen and Sun, Min and Liu, Maili and Li, Jingyuan and Tang, Chun
Journal: (2023)
Authors: Gong, Zhou and Zhu, Yueling and Lin, Shiyan and Meng, Ling-Shen and Sun, Min and Liu, Maili and Li, Jingyuan and Tang, Chun
Journal: (2023)
Spatiotemporal stop-and-go dynamics of the mitochondrial TOM core complex correlates with channel activity
Authors: Wang, Shuo and Findeisen, Lukas and Leptihn, Sebastian and Wallace, Mark I and H{\"o}rning, Marcel and Nussberger, Stephan
Journal: Communications biology (2022): 1--11
Authors: Wang, Shuo and Findeisen, Lukas and Leptihn, Sebastian and Wallace, Mark I and H{\"o}rning, Marcel and Nussberger, Stephan
Journal: Communications biology (2022): 1--11
Caveat fluorophore: an insiders’ guide to small-molecule fluorescent labels
Authors: Grimm, Jonathan B and Lavis, Luke D
Journal: Nature methods (2022): 149--158
Authors: Grimm, Jonathan B and Lavis, Luke D
Journal: Nature methods (2022): 149--158
References
View all 21 references: Citation Explorer
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
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
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
Authors: Freeman LM, Li S, Dayani Y, Choi HS, Malmstadt N, Armani AM.
Journal: Appl Phys Lett (2011): 143703
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
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
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
Authors: Volke D, Hoffmann R.
Journal: Electrophoresis (2008): 4516
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