iFluor® 514 maleimide

iFluor® 514 Maleimide is a green-fluorescent, thiol-reactive dye for selective covalent labeling of antibodies, proteins, peptides, 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 511 nm and emission at 527 nm.
Fluorescence Performance: Bright, photostable fluorescence with a quantum yield of 0.83.
Spectral Compatibility: Alternative to Alexa Fluor® 514 and rhodamine 6G.
Applications: Suitable for fluorescent conjugation of antibodies, peptides, and thiol-modified oligonucleotides.

Fluorescent dye maleimides (e.g., iFluor® 514 maleimide) 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
72500	1 mg	Price

Overview

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, 514, 555 and 633 nm). iFluor® 514 dyes have fluorescence excitation and emission maxima of ~510 nm and ~527 nm respectively. These spectral characteristics make them an excellent alternative to Alexa Fluor® 514 labeling dye and rhodamine 6G (Alexa Fluor® is the trademark of Invitrogen). For some antibody conjugates, iFluor® 514 conjugates are significantly brighter. iFluor® 514 Maleimide is stable and shows good reactivity and selectivity with protein thiol group.

Calculators

Common stock solution preparation

Table 1. Volume of DMSO needed to reconstitute specific mass of iFluor® 514 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	105.192 µL	525.961 µL	1.052 mL	5.26 mL	10.519 mL
5 mM	21.038 µL	105.192 µL	210.385 µL	1.052 mL	2.104 mL
10 mM	10.519 µL	52.596 µL	105.192 µL	525.961 µL	1.052 mL

Molarity calculator

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

Mass (Calculate)		Molecular weight		Volume (Calculate)		Concentration (Calculate)		Moles
mg	÷	950.64 g/mol	=	mL	x	mM	=	mmol

References

View all 3 references: Citation Explorer

Dual-axis confocal configuration for depth sensitive fluorescence spectroscopy.

Authors:

Lin, Yongping and Chang, Tse-Shao and Chen, Jing and Li, Gaoming

Journal:

Optics letters (2021): 3588-3591

Toxicity of organic fluorophores used in molecular imaging: literature review.

Authors:

Alford, Raphael and Simpson, Haley M and Duberman, Josh and Hill, G Craig and Ogawa, Mikako and Regino, Celeste and Kobayashi, Hisataka and Choyke, Peter L

Journal:

Molecular imaging (2009): 341-54

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

Physical properties

Molecular weight	950.64
Solvent	DMSO

Spectral properties

Absorbance (nm)	511
Correction factor (260 nm)	0.265
Correction factor (280 nm)	0.116
Extinction coefficient (cm ^-1 M ^-1)	75000 ¹
Excitation (nm)	511
Emission (nm)	527
Quantum yield	0.83 ¹

Usage and storage

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

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Page updated on October 23, 2026