logo
AAT Bioquest

iFluor® 450 maleimide

AAT Bioquest's iFluor® dyes are optimized for labeling proteins, particularly 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, 555, and 633 nm). Under the same conditions, iFluor® 450 dye conjugates are significantly brighter than the corresponding bioconjugates of other spectrally similar dyes. iFluor® 450 maleimide is stable and shows good reactivity and selectivity with the thiol group.

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

iFluor® 450 maleimide stock solution (Solution B)
  1. Add anhydrous DMSO into the vial of iFluor® 450 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.

Protein stock solution (Solution A)
  1. 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.

Disulfide Reduction (If Necessary)

If your protein does not contain a free cysteine, it must be treated with DTT or TCEP to generate a thiol group. DTT and TCEP are utilized to convert disulfide bonds into two free thiol groups. If using DTT, ensure to remove any free DTT via dialysis or gel filtration before conjugating a dye maleimide to your protein. Below is a sample protocol for generating a free thiol group:

  1. Prepare a fresh solution of 1 M DTT by dissolving 15.4 mg of DTT in 100 µL of distilled water.

  2. To prepare the IgG solution in 20 mM DTT, first, add 20 µL of DTT stock to each milliliter of the IgG solution while mixing gently. Then, allow the solution to stand at room temperature for 30 minutes without additional mixing. This resting period helps to minimize the reoxidation of cysteines to cystines.

  3. Pass the reduced IgG through a filtration column that has been pre-equilibrated with "Exchange Buffer." Collect 0.25 mL fractions as they elute from the column.

  4. Determine the protein concentrations and combine the fractions containing the highest amounts of IgG. This can be accomplished using either spectrophotometric or colorimetric methods.

  5. Proceed with the conjugation immediately after this step (refer to the Sample Experiment Protocol for details).

    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. 

  6. Item content

SAMPLE EXPERIMENTAL PROTOCOL

This labeling protocol was developed for the conjugate of Goat anti-mouse IgG with iFluor® 450 maleimide. You might need further optimization for your particular proteins.

Note: Each protein requires a specific dye-to-protein ratio, which varies based on the properties of the dyes. Over-labeling a protein can negatively impact its binding affinity while using a low dye-to-protein ratio can result in reduced sensitivity. 

Run the 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 Conjugate

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.

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 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 5-8 moles of iFluor® 450 maleimide to one mole of antibody. The following steps are used to determine the DOS of iFluor® 450 maleimide-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 = 502 nm for iFluor® 450 dyes)

For most spectrophotometers, the sample (from the column fractions) needs to be diluted with de-ionized water so that the OD 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 502 nm is the maximum absorption of iFluor® 450 maleimide. To obtain accurate DOS, make sure that 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

Spectrum

Product family

NameExcitation (nm)Emission (nm)Extinction coefficient (cm -1 M -1)Quantum yieldCorrection Factor (260 nm)Correction Factor (280 nm)
iFluor® 350 maleimide3454502000010.9510.830.23
iFluor® 488 maleimide4915167500010.910.210.11
iFluor® 555 maleimide55757010000010.6410.230.14
iFluor® 647 maleimide65667025000010.2510.030.03
iFluor® 680 maleimide68470122000010.2310.0970.094
iFluor® 700 maleimide69071322000010.2310.090.04
iFluor® 750 maleimide75777927500010.1210.0440.039
iFluor® 790 maleimide78781225000010.1310.10.09
iFluor® 800 maleimide80182025000010.1110.030.08
iFluor® 810 maleimide81182225000010.0510.090.15
iFluor® 820 maleimide82285025000010.110.16
iFluor® 860 maleimide85387825000010.10.14
iFluor® 532 maleimide5375609000010.6810.260.16
iFluor® 594 maleimide58760320000010.5310.050.04
iFluor® 405 maleimide4034273700010.9110.480.77
iFluor® 430 maleimide4334984000010.7810.680.3
iFluor® 568 maleimide56858710000010.5710.340.15
iFluor® 633 maleimide64065425000010.2910.0620.044
iFluor® 460 maleimide468493800001~0.810.980.46
iFluor® 665 maleimide667692110,00010.2210.120.09
iFluor® 450 Styramide *Superior Replacement for Opal Polaris 480*4515024000010.8210.450.27
iFluor® 450 Tyramide *Superior Replacement for Opal 480*4515024000010.8210.450.27
iFluor® 546 maleimide54155710000010.6710.250.15
iFluor® 840 maleimide8368792000001-0.20.09
iFluor® 770 maleimide77779725000010.160.090.08
iFluor® 780 maleimide78480825000010.1610.130.12
iFluor® 830 maleimide830867----
iFluor® 514 maleimide5115277500010.8310.2650.116
iFluor® 660 maleimide66367825000010.2610.070.08
iFluor® 670 maleimide67168220000010.5510.030.033
iFluor® 720 maleimide71674024000010.1410.150.13
Show More (22)

Citations

View all 3 citations: Citation Explorer
Deep Sequencing Analysis of the Eha-Regulated Transcriptome of Edwardsiella tarda Following Acidification
Authors: Gao, D and Liu, N and Li, Y and Zhang, Y and Liu, G and others, undefined
Journal: Metabolomics (Los Angel) (2017): 2153--0769
Suramin inhibits cullin-RING E3 ubiquitin ligases
Authors: Wu, Kenneth and Chong, Robert A and Yu, Qing and Bai, Jin and Spratt, Donald E and Ching, Kevin and Lee, Chan and Miao, Haibin and Tappin, Inger and Hurwitz, Jerard and others, undefined
Journal: Proceedings of the National Academy of Sciences (2016): E2011--E2018
Glycosaminoglycan mimicry by COAM reduces melanoma growth through chemokine induction and function
Authors: Piccard, Helene and Berghmans, Nele and Korpos, Eva and Dillen, Chris and Aelst, Ilse Van and Li, S and ra , undefined and Martens, Erik and Liekens, S and ra , undefined and Noppen, Sam and Damme, Jo Van and others, undefined
Journal: International Journal of Cancer (2012): E425--E436

References

View all 49 references: Citation Explorer
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
Visualizing dengue virus through Alexa Fluor labeling
Authors: Zhang S, Tan HC, Ooi EE.
Journal: J Vis Exp. (2011)
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
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
Page updated on October 8, 2024

Ordering information

Price
Unit size
Catalog Number1057
Quantity
Add to cart

Additional ordering information

Telephone1-800-990-8053
Fax1-800-609-2943
Emailsales@aatbio.com
InternationalSee distributors
Bulk requestInquire
Custom sizeInquire
Technical SupportContact us
Purchase orderSend to sales@aatbio.com
ShippingStandard overnight for United States, inquire for international
Request quotation

Physical properties

Molecular weight

527.55

Solvent

DMSO

Spectral properties

Correction Factor (260 nm)

0.45

Correction Factor (280 nm)

0.27

Extinction coefficient (cm -1 M -1)

400001

Excitation (nm)

451

Emission (nm)

502

Quantum yield

0.821

Storage, safety and handling

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

Storage

Freeze (< -15 °C); Minimize light exposure
UNSPSC12171501
HL-60 cells were incubated with (Red, +) or without (Green, -) Anti-human HLA-ABC (W6/32 mAb), followed by iFluor® 450 goat anti-mouse IgG conjugate. The fluorescence signal was monitored using ACEA NovoCyte flow cytometer in FITC channel.
HL-60 cells were incubated with (Red, +) or without (Green, -) Anti-human HLA-ABC (W6/32 mAb), followed by iFluor® 450 goat anti-mouse IgG conjugate. The fluorescence signal was monitored using ACEA NovoCyte flow cytometer in FITC channel.
HL-60 cells were incubated with (Red, +) or without (Green, -) Anti-human HLA-ABC (W6/32 mAb), followed by iFluor® 450 goat anti-mouse IgG conjugate. The fluorescence signal was monitored using ACEA NovoCyte flow cytometer in FITC channel.