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iFluor® 665 succinimidyl ester

Ordering information
Price ()
Catalog Number1550
Unit Size
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Additional ordering information
InternationalSee distributors
ShippingStandard overnight for United States, inquire for international
Physical properties
Molecular weight1210.53
Spectral properties
Correction Factor (260 nm)0.12
Correction Factor (280 nm)0.09
Extinction coefficient (cm -1 M -1)110,0001
Excitation (nm)667
Emission (nm)692
Quantum yield0.221
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
Alternative formats
iFluor® 665 maleimide


Molecular weight
Correction Factor (260 nm)
Correction Factor (280 nm)
Extinction coefficient (cm -1 M -1)
Excitation (nm)
Emission (nm)
Quantum yield
AAT Bioquest's iFluor® dyes are optimized for labeling proteins, in particular, antibodies. These dyes are bright, photostable and have minimal quenching on proteins. They can be well excited by the major laser lines of fluorescence instruments (e.g., 350, 405, 488, 532, 555, 633 and 647 nm). iFluor® 665 family has the spectral properties similar to those of Alexa Fluor® 660 (Alexa Fluor® is the trademark of Invitrogen). iFluor® 665 family has fluorescence that is pH-independent from pH 3 to 11. These spectral characteristics make this new dye family an excellent alternative to Alexa Fluor® 660. Under the same conditions, iFluor® 665 gives stronger fluorescence signal on some antibodies we tested. iFluor® 665 SE is reasonably stable and shows good reactivity and selectivity with protein amino groups.

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. iFluor™ 665 SE stock solution (Solution B)
Add anhydrous DMSO into the vial of iFluor™ 665 SE 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 iFluor™ 665 SE. 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 iFluor® 665 succinimidyl 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 mM82.608 µL413.042 µL826.084 µL4.13 mL8.261 mL
5 mM16.522 µL82.608 µL165.217 µL826.084 µL1.652 mL
10 mM8.261 µL41.304 µL82.608 µL413.042 µL826.084 µL

Molarity calculator

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Spectral properties

Correction Factor (260 nm)0.12
Correction Factor (280 nm)0.09
Extinction coefficient (cm -1 M -1)110,0001
Excitation (nm)667
Emission (nm)692
Quantum yield0.221

Product family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)
iFluor® 350 succinimidyl ester3454502000010.9510.830.23
iFluor® 405 succinimidyl ester4034273700010.9110.480.77
iFluor® 430 succinimidyl ester4334984000010.7810.680.3
iFluor® 440 succinimidyl ester4344804000010.6710.3520.229
iFluor® 450 succinimidyl ester4515024000010.8210.450.27
iFluor® 460 succinimidyl ester468493800001~0.810.980.46
iFluor® 488 succinimidyl ester4915167500010.910.210.11
iFluor® 514 succinimidyl ester5115277500010.8310.2650.116
iFluor® 532 succinimidyl ester5375609000010.6810.260.16
iFluor® 546 succinimidyl ester54155710000010.6710.250.15
iFluor® 555 succinimidyl ester55757010000010.6410.230.14
iFluor® 560 succinimidyl ester56057112000010.5710.04820.069
iFluor® 568 succinimidyl ester56858710000010.5710.340.15
iFluor® 570 succinimidyl ester56057112000010.5810.0480.069
iFluor® 594 succinimidyl ester58860418000010.5310.050.04
iFluor® 597 succinimidyl ester59861810000010.710.3350.514
iFluor® 610 succinimidyl ester61062811000010.8510.320.49
iFluor® 633 succinimidyl ester64065425000010.2910.0620.044
iFluor® 647 succinimidyl ester65667025000010.2510.030.03
iFluor® 660 succinimidyl ester66367825000010.2610.070.08
iFluor® 670 succinimidyl ester67168220000010.5510.030.033
iFluor® 680 succinimidyl ester68470122000010.2310.0970.094
iFluor® 690 succinimidyl ester68570422000010.3010.090.06
iFluor® 700 succinimidyl ester69071322000010.2310.090.04
iFluor® 710 succinimidyl ester71773919000010.6010.120.07
iFluor® 720 succinimidyl ester71674024000010.1410.150.13
iFluor® 740 succinimidyl ester74276422500010.2010.160.16
iFluor® 750 succinimidyl ester75777927500010.1210.0440.039
iFluor® 770 succinimidyl ester77779725000010.160.090.08
iFluor® 780 succinimidyl ester78480825000010.1610.130.12
iFluor® 790 succinimidyl ester78781225000010.1310.10.09
iFluor® 800 succinimidyl ester80182025000010.1110.030.08
iFluor® 810 succinimidyl ester81182225000010.0510.090.15
iFluor® 820 succinimidyl ester8228502500001-0.110.16
iFluor® 830 succinimidyl ester830867----
iFluor® 840 succinimidyl ester8368792000001-0.20.09
iFluor® 860 succinimidyl ester8538782500001-0.10.14
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Recognition of Invasive Prostate Cancer Using a GHRL Polypeptide Probe Targeting GHSR in a Mouse Model In Vivo.
Authors: Ye, Huamao and Yang, Yue and Chen, Rui and Shi, Xiaolei and Fang, Yu and Yang, Jun and Dong, Yuanzhen and Chen, Lili and Xia, Jianghua and Wang, Chao and Yang, Chenghua and Feng, Jun and Wang, Yang and Feng, Xiang and Lü, Chen
Journal: Current pharmaceutical design (2020): 1614-1621
Reengineering the optical absorption cross-section of photosynthetic reaction centers.
Authors: Dutta, Palash K and Lin, Su and Loskutov, Andrey and Levenberg, Symon and Jun, Daniel and Saer, Rafael and Beatty, J Thomas and Liu, Yan and Yan, Hao and Woodbury, Neal W
Journal: Journal of the American Chemical Society (2014): 4599-604
A rapid sensitive, flow cytometry-based method for the detection of Plasmodium vivax-infected blood cells.
Authors: Roobsoong, Wanlapa and Maher, Steven P and Rachaphaew, Nattawan and Barnes, Samantha J and Williamson, Kim C and Sattabongkot, Jetsumon and Adams, John H
Journal: Malaria journal (2014): 55
Comparison of a chimeric anti-carcinoembryonic antigen antibody conjugated with visible or near-infrared fluorescent dyes for imaging pancreatic cancer in orthotopic nude mouse models.
Authors: Maawy, Ali A and Hiroshima, Yukihiko and Kaushal, Sharmeela and Luiken, George A and Hoffman, Robert M and Bouvet, Michael
Journal: Journal of biomedical optics (2013): 126016
Nucleic acid sandwich hybridization assay with quantum dot-induced fluorescence resonance energy transfer for pathogen detection.
Authors: Chou, Cheng-Chung and Huang, Yi-Han
Journal: Sensors (Basel, Switzerland) (2012): 16660-72
Single-molecule dynamics of phytochrome-bound fluorophores probed by fluorescence correlation spectroscopy.
Authors: Miller, Abigail E and Fischer, Amanda J and Laurence, Ted and Hollars, Christopher W and Saykally, Richard J and Lagarias, J Clark and Huser, Thomas
Journal: Proceedings of the National Academy of Sciences of the United States of America (2006): 11136-41
A far-red fluorescent contrast agent to image epidermal growth factor receptor expression.
Authors: Hsu, Elizabeth R and Anslyn, Eric V and Dharmawardhane, Su and Alizadeh-Naderi, Reza and Aaron, Jesse S and Sokolov, Konstantin V and El-Naggar, Adel K and Gillenwater, Ann M and Richards-Kortum, Rebecca R
Journal: Photochemistry and photobiology (2004): 272-9