5(6)-Carboxyfluorescein

5(6)-Carboxyfluorescein is a mixture of 5-carboxy and 6-carboxy derivatives of fluorescein. It is commonly used to label biomolecules through a reaction involving the carboxyl group. Unlike its succinimidyl ester derivative CFSE (Cay-14456), 5(6)-carboxyfluorescein is membrane impermeant. As a result, it can be used in studies of membrane permeability. 5(6)-Carboxyfluorescein displays excellent fluorescence (excitation/emission at 492/514 nm, respectively), and its excitation maximum closely matches the 488 nm spectral line of argon-ion lasers.Formal Name: 3',6'-dihydroxy-3-oxo-spiro[isobenzofuran-1(3H),9'-[9H]xanthene]-ar-carboxylic acid. CAS Number: 72088-94-9. Synonyms: 5(6)-FAM. Molecular Formula: C21H12O7. Formula Weight: 376.3. Purity: >90% (mixture of isomers). Emission: 514 nm. Excitation: 492 nm. Formulation: (Request formulation change), A crystalline solid. Solubility: DMF: 1 mg/ml, DMSO: 0.5 mg/ml, Ethanol: 5 mg/ml, Ethanol:PBS(pH 7.2) (1:1): 0.5 mg/ml. lambdamax: 209, 225, 277 nm. SMILES: OC1=CC=C(C2(C(C=CC(C(O)=O)=C3)=C3C(O2)=O)C(C=CC(O)=C4)=C4O5)C5=C1.OC6=CC=C(C7(C(C=C(C(O)=O)C=C8)=C8C(O7)=O)C(C=CC(O)=C9)=C9O%10)C%10=C6. InChi Code: InChI=1S/2C21H12O7/c22-11-2-5-15-17(8-11)27-18-9-12(23)3-6-16(18)21(15)14-4-1-10(19(24)25)7-13(14)20(26)28-21,22-11-2-5-14-17(8-11)27-18-9-12(23)3-6-15(18)21(14)16-7-10(19(24)25)1-4-13(16)20(26)28-21/h2*1-9,22-23H,(H,24,25). InChi Key: BPVHBBXCESDRKW-UHFFFAOYSA-N.