iFluor® 750 maleimide

AAT Bioquest's iFluor® dyes are developed for labeling proteins, particularly antibodies. These dyes are optimized to have minimal fluorescence quenching effect on proteins and nucleic acids. Our iFluor® 750 dyes have fluorescence excitation and emission maxima of ~757 nm and ~779 nm, respectively, with good photostability. Our in-house comparable studies indicated that our iFluor® 750 dyes are significantly brighter than the corresponding Cy7® and Alexa Fluor® 750. These spectral characteristics make them a superior alternative to Cy7® and Alexa Fluor® 750 (Cy7® and Alexa Fluor® are the trademarks of GE Healthcare and Invitrogen). iFluor® 780 conjugates have been widely used in fluorescence animal imaging applications. The iFluor® 750 maleimide is reasonably 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.

1. iFluor™ 750 maleimide stock solution (Solution B)

Add anhydrous DMSO into the vial of iFluor™ 750 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.
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 iFluor™ 750 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.

Spectrum

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Product family

Name	Excitation (nm)	Emission (nm)	Extinction coefficient (cm ^-1 M ^-1)	Quantum yield	Correction Factor (260 nm)	Correction Factor (280 nm)
iFluor® 350 maleimide	345	450	20000¹	0.95¹	0.83	0.23
iFluor® 488 maleimide	491	516	75000¹	0.9¹	0.21	0.11
iFluor® 555 maleimide	557	570	100000¹	0.64¹	0.23	0.14
iFluor® 647 maleimide	656	670	250000¹	0.25¹	0.03	0.03
iFluor® 680 maleimide	684	701	220000¹	0.23¹	0.097	0.094
iFluor® 700 maleimide	690	713	220000¹	0.23¹	0.09	0.04
iFluor® 790 maleimide	787	812	250000¹	0.13¹	0.1	0.09
iFluor® 800 maleimide	801	820	250000¹	0.11¹	0.03	0.08
iFluor® 810 maleimide	811	822	250000¹	0.05¹	0.09	0.15
iFluor® 820 maleimide	822	850	250000¹		0.11	0.16
iFluor® 860 maleimide	853	878	250000¹		0.1	0.14
iFluor® 532 maleimide	537	560	90000¹	0.68¹	0.26	0.16
iFluor® 594 maleimide	587	603	200000¹	0.53¹	0.05	0.04
iFluor® 405 maleimide	403	427	37000¹	0.91¹	0.48	0.77
iFluor® 430 maleimide	433	498	40000¹	0.78¹	0.68	0.3
iFluor® 568 maleimide	568	587	100000¹	0.57¹	0.34	0.15
iFluor® 633 maleimide	640	654	250000¹	0.29¹	0.062	0.044
iFluor® 450 maleimide	451	502	40000¹	0.82¹	0.45	0.27
iFluor® 750 Styramide Superior Replacement for Alexa Fluor 750 tyramide	757	779	275000¹	0.12¹	0.044	0.039
iFluor® 460 maleimide	468	493	80000¹	~0.8¹	0.98	0.46
iFluor® 665 maleimide	667	692	110,000¹	0.22¹	0.12	0.09
iFluor® 546 maleimide	541	557	100000¹	0.67¹	0.25	0.15
iFluor® 840 maleimide	836	879	200000¹	-	0.2	0.09
iFluor® 770 maleimide	777	797	250000¹	0.16	0.09	0.08
iFluor® 780 maleimide	784	808	250000¹	0.16¹	0.13	0.12
iFluor® 830 maleimide	830	867	-	-	-	-
iFluor® 514 maleimide	511	527	75000¹	0.83¹	0.265	0.116
iFluor® 660 maleimide	663	678	250000¹	0.26¹	0.07	0.08
iFluor® 670 maleimide	671	682	200000¹	0.55¹	0.03	0.033
iFluor® 720 maleimide	716	740	240000¹	0.14¹	0.15	0.13
iFluor® 560 maleimide	560	571	120000¹	0.57¹	0.0482	0.069
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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 November 21, 2024

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Physical properties

Molecular weight	~1100
Solvent	DMSO

Spectral properties

Correction Factor (260 nm)	0.044
Correction Factor (280 nm)	0.039
Correction Factor (565 nm)	0.0250
Correction Factor (650 nm)	0.1413
Extinction coefficient (cm ^-1 M ^-1)	275000¹
Excitation (nm)	757
Emission (nm)	779
Quantum yield	0.12¹

Storage, safety and handling

H-phrase	H303, H313, H333
Hazard symbol	XN
Intended use	Research Use Only (RUO)
R-phrase	R20, R21, R22
Storage	Freeze (< -15 °C); Minimize light exposure
UNSPSC	12171501