CAS No. 3326-32-7

Batch: Purity:98.88
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Fluorescein-5-isothiocyanate (FITC) Chemical Structure
Chemical Structure
Check the Fluorescein-5-isothiocyanate (FITC) product page for in-depth specifications, including solubility, stock solutions, MOA, and working concentrations.

Chemical Information

CAS Number 3326-32-7
Molecular Formula

C21H11NO5S
Molecular Weight (MW) 389.38
SMILES OC1=CC2=C(C=C1)C3(OC(=O)C4=C3C=CC(=C4)N=C=S)C5=C(O2)C=C(O)C=C5

Ordering Information

Biological Activity

Fluorescein-5-isothiocyanate (FITC) is an amine-reactive fluorescent probe widely used for labeling proteins, peptides, and antibodies. The molecule features an isothiocyanate functional group that selectively reacts with primary amine groups on target biomolecules to form stable thiourea linkages. This conjugation enables fluorescent visualization and tracking of conjugated targets across applications such as immunofluorescence microscopy, flow cytometry, and ligand-binding assays.

Solubility

Batch:
All in vitro solubility values are batch-tested experimental data (non-literature values).
Solvent Solubility & Note
DMSO 78 mg/mL (200.31 mM)
(Moisture-contaminated DMSO may reduce solubility. Use fresh, anhydrous DMSO. The recommended stock concentration is 10 mM in DMSO.)
Ethanol 10 mg/mL
Water Insoluble
FAQ
Q: Why does a DMSO stock precipitate in media/saline?
A: It is caused by unheated aqueous media (supersaturation), local solvent shock, or incorrect mixing sequence.
How to fix it?
  • Preheat media/saline to 37°C.
  • Mix rapidly (pipette/vortex) upon addition.
  • For complex mixes, always add the aqueous phase last.
  • Re-dissolve minor precipitates with a 37°C water bath and sonication (≤30 min).

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Note: Technical data last updated: Sep 1, 2026.