Name: iFluor® 540 maleimide
Brand: AAT Bioquest
SKU: 1427
Price: 237 USD
Availability: InStock

iFluor® 540 maleimide

iFluor® 540 Maleimide is a thiol-reactive fluorescent dye for selective covalent labeling of antibodies, proteins, and other thiol-containing biomolecules in fluorescence-based research applications.

Thiol-Reactive Functionality: Maleimide group selectively reacts with free thiols, including cysteine residues.
Spectral Properties: Excitation at 540 nm and emission at 557 nm.
Fluorescence Performance: Emits a bright red fluorescence when excited around 530-545 nm.
Applications: Suitable for fluorescent conjugation of reduced antibodies, peptides, and thiol-modified oligonucleotides.

Fluorescent dye maleimides are the most popular tool for conjugating dyes to a peptide, protein, antibody, thiol-modified oligonucleotide or nucleic acid through their SH group. Maleimides react readily with the thiol group of proteins, thiol-modified oligonucleotides, and other thiol-containing molecules under neutral conditions. The resulting dye conjugates are quite stable.

Protocol

SDS

Catalog	Size	Price	Quantity
1427	1 mg	Price

Overview

iFluor® 540 maleimide selectively reacts with thiol group of a biomolecule. It is widely used to label the reduced antibodies and other thiol-containing biomolecules such as peptides and thiol-modified oligos. iFluor®540 is a fluorophore from the iFluor® family, which is known for its bright red fluorescence and compatibility with various fluorescence techniques and instruments. When excited with light in the green to yellow range (around 530 to 545 nm), iFluor® 540 emits red fluorescence with an emission peak typically around 560 to 570 nanometers. iFluor® 540 can be conjugated to a variety of biomolecules, including antibodies, proteins, nucleic acids, and small molecules, enabling their visualization and tracking in cells and tissues. It is commonly used in fluorescence microscopy, immunohistochemistry, flow cytometry, and other fluorescence-based assays.

Calculators

Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of iFluor® 540 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	128.564 µL	642.822 µL	1.286 mL	6.428 mL	12.856 mL
5 mM	25.713 µL	128.564 µL	257.129 µL	1.286 mL	2.571 mL
10 mM	12.856 µL	64.282 µL	128.564 µL	642.822 µL	1.286 mL

Molarity calculator

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

Mass (Calculate)		Molecular weight		Volume (Calculate)		Concentration (Calculate)		Moles
mg	÷	777.82 g/mol	=	mL	x	mM	=	mmol

References

View all 8 references: Citation Explorer

A molecular rack and pinion actuates a cell-surface adhesin and enables bacterial gliding motility.

Authors:

Shrivastava, Abhishek and Berg, Howard C

Journal:

Science advances (2020): eaay6616

Protein Environment and DNA Orientation Affect Protein-Induced Cy3 Fluorescence Enhancement.

Authors:

Nguyen, Binh and Ciuba, Monika A and Kozlov, Alexander G and Levitus, Marcia and Lohman, Timothy M

Journal:

Biophysical journal (2019): 66-73

Electrical readout of protein microarrays on regular glass slides.

Authors:

Bonilla, Diana and Mallén, Maria and de la Rica, Roberto and Fernández-Sánchez, César and Baldi, Antonio

Journal:

Analytical chemistry (2011): 1726-31

Toward a solid-phase nucleic acid hybridization assay within microfluidic channels using immobilized quantum dots as donors in fluorescence resonance energy transfer.

Authors:

Chen, Lu and Algar, W Russ and Tavares, Anthony J and Krull, Ulrich J

Journal:

Analytical and bioanalytical chemistry (2011): 133-41

Thiazole orange and Cy3: improvement of fluorescent DNA probes with use of short range electron transfer.

Authors:

Menacher, Florian and Rubner, Moritz and Berndl, Sina and Wagenknecht, Hans-Achim

Journal:

The Journal of organic chemistry (2008): 4263-6

Physical properties

Molecular weight	777.82
Solvent	DMSO

Spectral properties

Correction factor (260 nm)	0.26
Correction factor (280 nm)	0.105
Extinction coefficient (cm ^-1 M ^-1)	80,000
Excitation (nm)	540
Emission (nm)	557
Quantum yield	0.63

Usage and storage

Intended use	Research Use Only (RUO)
Storage	Freeze (< -15 °C); Minimize light exposure

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Page updated on October 24, 2026