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iFluor® 488 succinimidyl ester

Although FITC is still the most popular fluorescent labeling dye for preparing green fluorescent bioconjugates, there are certain limitations with FITC, such as severe photobleaching for microscope imaging and pH-sensitive fluorescence. Protein conjugates prepared with iFluor® 488 dyes are far superior to conjugates of fluorescein derivatives such as FITC. iFluor® 488 conjugates are significantly brighter than fluorescein conjugates and are much more photostable. Additionally, the fluorescence of iFluor® 488 is not affected by pH (4-10). This pH insensitivity is a major improvement over fluorescein, which emits its maximum fluorescence only at pH above 9. iFluor® 488 SE dye is reasonably stable and shows good reactivity and selectivity with protein amino groups. This iFluor® 488 has spectral properties and reactivity similar to Alexa Fluor® 488 NHS ester ( Alexa Fluor® is the trademark of Invitrogen).

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

Protein stock solution (Solution A)
  1. Mix 100 µL of a reaction buffer (e.g., 1 M  sodium bicarbonate solution or 1 M phosphate buffer with pH ~8.5 to 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. The final protein concentration range of 2-10 mg/mL is recommended for optimal labeling efficiency.

iFluor® 488 SE stock solution (Solution B)
  1. Add anhydrous DMSO into the vial of iFluor® 488 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 the freezer for two weeks when kept from light and moisture. Avoid freeze-thaw cycles.

SAMPLE EXPERIMENTAL PROTOCOL

This labeling protocol was developed for the conjugate of Goat anti-mouse IgG with iFluor® 488 SE. You might need further optimization for your particular proteins.

Note: Each protein requires a distinct dye/protein ratio, which also depends on the properties of dyes. Over-labeling of a protein could detrimentally affect its binding affinity, while the protein conjugates of low dye/protein ratio give reduced sensitivity.

Run conjugation reaction
  1. Use a 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 using a 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 must be diluted with staining buffer, and aliquoted for multiple uses.

    Note: For longer-term storage, the dye-protein conjugate solution needs to be concentrated or freeze-dried.

Characterize the Desired Dye-Protein Conjugate

The Degree of Substitution (DOS) is the most important factor for characterizing dye-labeled protein. Proteins of lower DOS usually have weaker fluorescence intensity, but proteins of higher DOS (e.g., DOS > 6) tend to have reduced fluorescence too. The optimal DOS for most antibodies is recommended between 2 and 10, depending on the properties of dye and protein. For effective labeling, the degree of substitution should be controlled to have 6-8 moles of iFluor® 488 SE to one mole of antibody. The following steps are used to determine the DOS of iFluor® 488 SE labeled proteins.

Measure absorption

To measure the absorption spectrum of a dye-protein conjugate, it is recommended to keep the sample concentration in the range of 1-10 µM depending on the extinction coefficient of the dye.

Read OD (absorbance) at 280 nm and dye maximum absorption (ƛmax = 490 nm for iFluor® 488 dye)

For most spectrophotometers, the sample (from the column fractions) needs to be diluted with de-ionized water so that the O.D. values are in the range of 0.1 to 0.9. The O.D. (absorbance) at 280 nm is the maximum absorption of protein, while 490 nm is the maximum absorption of iFluor® 488 SE. To obtain accurate DOS, ensure the conjugate is free of the non-conjugated dye. 

Calculate DOS

You can calculate DOS using our tool by following this link: https://www.aatbio.com/tools/degree-of-labeling-calculator

Calculators

Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of iFluor® 488 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 mM105.812 µL529.061 µL1.058 mL5.291 mL10.581 mL
5 mM21.162 µL105.812 µL211.625 µL1.058 mL2.116 mL
10 mM10.581 µL52.906 µL105.812 µL529.061 µL1.058 mL

Molarity calculator

Enter any two values (mass, volume, concentration) to calculate the third.

Mass (Calculate)Molecular weightVolume (Calculate)Concentration (Calculate)Moles
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Spectrum

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® 514 succinimidyl ester5115277500010.8310.2650.116
iFluor® 532 succinimidyl ester5375609000010.6810.260.16
iFluor® 555 succinimidyl ester55757010000010.6410.230.14
iFluor® 594 succinimidyl ester58760320000010.5310.050.04
iFluor® 633 succinimidyl ester64065425000010.2910.0620.044
iFluor® 647 succinimidyl ester65667025000010.2510.030.03
iFluor® 660 succinimidyl ester66367825000010.2610.070.08
iFluor® 680 succinimidyl ester68470122000010.2310.0970.094
iFluor® 700 succinimidyl ester69071322000010.2310.090.04
iFluor® 750 succinimidyl ester75777927500010.1210.0440.039
iFluor® 610 succinimidyl ester61062811000010.8510.320.49
iFluor® 710 succinimidyl ester71673915000010.6010.120.07
iFluor® 790 succinimidyl ester78781225000010.1310.10.09
iFluor® 800 succinimidyl ester80182025000010.1110.030.08
iFluor® 810 succinimidyl ester81182225000010.0510.090.15
iFluor® 820 succinimidyl ester82285025000010.110.16
iFluor® 860 succinimidyl ester85387825000010.10.14
iFluor® 546 succinimidyl ester54155710000010.6710.250.15
iFluor® 568 succinimidyl ester56858710000010.5710.340.15
iFluor® 430 succinimidyl ester4334984000010.7810.680.3
iFluor® 450 succinimidyl ester4515024000010.8210.450.27
iFluor® 840 succinimidyl ester8368792000001-0.20.09
iFluor® 560 succinimidyl ester56057112000010.5710.04820.069
iFluor® 670 succinimidyl ester67168220000010.5510.030.033
iFluor® 460 succinimidyl ester468493800001~0.810.980.46
iFluor® 440 succinimidyl ester4344804000010.6710.3520.229
iFluor® 665 succinimidyl ester667692110,00010.2210.120.09
iFluor® 690 succinimidyl ester68570422000010.3010.090.06
iFluor® 720 succinimidyl ester71674024000010.1410.150.13
iFluor® 740 succinimidyl ester74076422500010.2010.160.16
iFluor® 597 succinimidyl ester59861810000010.710.3350.514
iFluor® 770 succinimidyl ester77779725000010.160.090.08
iFluor® 780 succinimidyl ester78480825000010.1610.130.12
iFluor® 570 succinimidyl ester55757012000010.581--
iFluor® 830 succinimidyl ester830867----
iFluor® 675 succinimidyl ester683700---0.066
iFluor® 620 succinimidyl ester621636---0.04
iFluor® 605 succinimidyl ester603623----
iFluor® 625 succinimidyl ester624640----
iFluor® 510 succinimidyl ester511530----
iFluor® 540 succinimidyl ester540557---0.105
iFluor® 445 succinimidyl ester446558----
iFluor® 500 succinimidyl ester501520----
Show More (36)

Citations

View all 69 citations: Citation Explorer
Vibrational Markers of Circulating Metastatic Cells LLC-R9
Authors: Gnatyuk, Olena Petrivna and Kolesnyk, Denys Leonidovych and Voitsitskyi, Taras and Karakhim, Sergiy Olexandrovych and Nikolenko, Andrii and Dementjev, Andrej S and Solyanik, Galina Ivanivna and Dovbeshko, Galina Ivanivna
Journal: (2024)
B-067 Human IgE Monoclonal Antibodies as Unique Tools for Allergy Diagnostics
Authors: Filep, S and Reid Black, K and Smith, B and Bermingham, M and Pomes, A and Chapman, M
Journal: Clinical Chemistry (2024): hvae106--429
B-065 Comparative Analysis of 14-3-3$\eta$ Autoantibody Assays on Luminex Platform for Diagnosing Axial Spondyloarthritis
Authors: Sidhu, N and Maksymowych, WP and Wichuk, S and Marotta, A
Journal: Clinical Chemistry (2024): hvae106--427
B-066 VeraBIND™ Borrelia Antibody Test: Multiplex Capture, Enrichment, and Detection of Borrelia Burgdorferi Antigens-Specific Immunoglobulins From Saline Oral Rinse Samples
Authors: Shamsundar, K and Ansari, KI and Bergmann, S and Kleven, K and Soldo, J
Journal: Clinical Chemistry (2024): hvae106--428
Alteration of Neuropilin-1 and Heparan Sulfate Interaction Impairs Murine B16 Tumor Growth
Authors: Painter, Chelsea D and Sankaranarayanan, Nehru Viji and Nagarajan, Balaji and Mandel Clausen, Thomas and West, Alan MV and Setiawan, Nicollette J and Park, Jeeyoung and Porell, Ryan N and Bartels, Phillip L and Sandoval, Daniel R and others,
Journal: ACS Chemical Biology (2024)

References

View all 49 references: Citation Explorer
Neuroanatomical basis of clinical joint application of "Jinggu" (BL 64, a source-acupoint) and "Dazhong" (KI 4, a Luo-acupoint) in the rat: a double-labeling study of cholera toxin subunit B conjugated with Alexa Fluor 488 and 594
Authors: Cui JJ, Zhu XL, Ji CF, Jing XH, Bai WZ.
Journal: Zhen Ci Yan Jiu (2011): 262
Simultaneous detection of virulence factors from a colony in diarrheagenic Escherichia coli by a multiplex PCR assay with Alexa Fluor-labeled primers
Authors: Kuwayama M, Shigemoto N, Oohara S, Tanizawa Y, Yamada H, Takeda Y, Matsuo T, Fukuda S.
Journal: J Microbiol Methods (2011): 119
Fluorescent "Turn-on" system utilizing a quencher-conjugated peptide for specific protein labeling of living cells
Authors: Arai S, Yoon SI, Murata A, Takabayashi M, Wu X, Lu Y, Takeoka S, Ozaki M.
Journal: Biochem Biophys Res Commun (2011): 211
Visualizing dengue virus through Alexa Fluor labeling
Authors: Zhang S, Tan HC, Ooi EE.
Journal: J Vis Exp. (2011)
Sequential ordering among multicolor fluorophores for protein labeling facility via aggregation-elimination based beta-lactam probes
Authors: Sadhu KK, Mizukami S, Watanabe S, Kikuchi K.
Journal: Mol Biosyst (2011): 1766
Page updated on November 1, 2024

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Physical properties

Molecular weight

945.07

Solvent

DMSO

Spectral properties

Correction Factor (260 nm)

0.21

Correction Factor (280 nm)

0.11

Extinction coefficient (cm -1 M -1)

750001

Excitation (nm)

491

Emission (nm)

516

Quantum yield

0.91

Storage, safety and handling

Certificate of OriginDownload PDF
H-phraseH303, H313, H333
Hazard symbolXN
Intended useResearch Use Only (RUO)
R-phraseR20, R21, R22

Storage

Freeze (< -15 °C); Minimize light exposure
UNSPSC12171501