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Fura-2, Pentaammonium Salt

Fura-2, pentaammonium salt is a membrane-impermeant ratiometric calcium indicator. It can be loaded into cells via microinjection or scrape loading.

Product Attributes

Cell permeability

Membrane impermeant

Indicator type



363/512 nm (no Ca2+); 335/505 nm (high Ca2+)

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Catalog #
1 mg
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Product Description

Fura-2, pentaammonium salt is a ratiometric fluorescent dye that binds to free intracellular calcium. It is membrane-impermeant and may be loaded into cells via microinjection or scrape loading.

Fura-2 fluorescence can be detected using flow cytometry, fluorescence microscopy, or certain fluoresence microplate readers. Upon calcium binding, the fluorescent excitation maximum of the indicator undergoes a blue shift from 363 nm (Ca2+-free) to 335 nm (Ca2+-saturated), while the fluorescence emission maximum is relatively unchanged at ~510 nm. A major use of Fura-2 is in drug discovery, for measuring intracellular calcium mobilization after activation of G protein-coupled receptors (GPCRs) and calcium channels.

  • Light yellow solid soluble in DMSO
  • Store at 4°C and protect from light, especially in solution
  • Kd: 145 nM (22°C in pH 7.2 buffer)
  • λExEm (no Ca2+) = 363/512 nm; λExEm (high Ca2+) = 335/505 nm
  • ε (363 nm, no Ca2+) = 27,000 M-1cm-1; ε (335 nm, high Ca2+) = 35,000 M-1cm-1
  • C29H37N8O14
  • MW: 721



BAPTA-based ion indicators like Fura-2 have been shown to be fixable in situ by EDC/EDAC (cat# 59002). The fixation of indicator dyes is useful for downstream immunofluorescence and IHC studies (Cell Calcium 1997, 21(3), 175).

As the indicator does not covalently bind to cellular components, it may be actively effluxed from the cell by organic anion transporters. The rate of efflux increases with temperature, and may vary between cell types, resulting in variable retention times of a few minutes to hours. Experiments using indicators in cells usually are performed within one or two hours of loading, but it may be possible to re-load cells with indicator if needed. The organic anion transporter inhibitor Probenecid (#50027) can be used to slow the rate of indicator efflux from cells.

Fura-2 Products


Unit Size

Catalog Number

Fura-2, pentaammonium salt1 mg50030
Fura-2, pentapotassium salt1 mg50031
Fura-2, pentasodium salt1 mg50032
Fura-2, AM ester10 x 100 ug50033
20 x 50 ug50033-1
1 mg50034
Fura-2, AM ester, 1 mM solution1 mL50029


  1. Am J Physiol 263, 1292 (1992), DOI: 10.1152/ajpheart.1992.263.4.H1292
  2. J Mol Cell Cardiol 24, 937 (1992), DOI: 10.1016/0022-2828(92)91861-X
  3. Methods Cell Biol, 99, 113, (2021), DOI: 10.1016/B978-0-12-374841-6.00005-0

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