Description
5/6-FAM – High-Purity Mixed-Isomer Fluorescein Dye for Versatile Bioconjugation
5/6-Carboxyfluorescein (5/6-FAM) is a high-purity, non-activated fluorescein dye available as a mixed-isomer preparation. Widely used for covalent labeling of proteins and alkylamino-modified oligonucleotides, it combines excellent fluorescence performance with robust compatibility across common labeling workflows. With excitation near 488 nm, 5/6-FAM is an ideal fluorophore for confocal microscopy and flow cytometry, offering strong signal intensity and high photostability.
Performance Highlights
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High-purity, non-activated fluorescein dye (mixed isomers)
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Excitation/emission maxima: 493 nm / 513 nm
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High absorptivity (ε > 81,000 M⁻¹·cm⁻¹)
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Excellent fluorescence quantum yield and solubility
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Suitable for FACS, microscopy, and custom bioconjugation
Properties
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Molecular Weight: 376.32
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Empirical Formula: C₂₁H₁₂O₇
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CAS Number: 72088-94-9
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Absorption [λmax]: 493 ± 3 nm
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Emission [λmax]: 513 ± 3 nm
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Extinction Coefficient (ε): >81,000 M⁻¹·cm⁻¹
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Excitation Source: 493–494 nm (compatible with 488 nm Ar-ion laser)
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Reactive Moiety: Free carboxylic acid
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Solubility: pH > 6, DMF, DMSO
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Buffer System for Fluorescence Readings: T&S Buffer, pH 9
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Appearance: Orange solid (powder)
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Storage: Room temperature; keep dry and protected from light (especially in solution)
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Trade Name: 5/6-Carboxyfluorescein; 5/6-FAM; 5-(and 6)-carboxyfluorescein, mixed isomers
Application
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Bioconjugation of antibodies, proteins, and modified nucleic acids
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Confocal laser scanning microscopy
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Flow cytometry (FACS)
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General fluorescence detection and imaging applications
