O COONa O NaO O 2 N NO 2 Br BrCA Index Name Spiro[isobenzofuran-1(3H),9 0 -[9H] xanthen]-3-one, 4 0 ,5 0 -dibromo-3 0 ,6 0 -dihydroxy-2 0 ,7 0 -dinitro-, sodium salt (1 : 2) Other Names Fluorescein, 4 0 ,disodium salt; C.I. 45400; C.I. Acid Red 91; Dibromodinitrofluorescein sodium; Eosin B; Eosin BA; Eosine B; Eosine BA; Eosine BN; Eosine BNX; Eosine I Bluish; Saffrosine; Simacid Nitro Eosin 24669 Merck Index Number 3602 Chemical/Dye Class Xanthene Molecular Formula C 20 H 6 Br 2 N 2 Na 2 O 9 Molecular Weight 624.06 Physical Form Red-brown to green crystals or powder Solubility Freely soluble in water; soluble in ethanol Melting Point 295 C Absorption (l max ) 514 nm, 395 nm Emission (l max ) 544 nm Synthesis Synthetic method 1-4 Staining Applications Brain; 5 cells; 6 microorganisms; 7 nucleic acids; 8 peptides; 9 proteins; 9-13 enzyme substrates; 14,15 hairs 16 Sakamoto, H. Development of a colorimetric quantitation method of protein in solution by excluding the influence of creatinine. PCT Int. Appl. WO 2005071420, 2005; Chem. Abstr. 2005, 143, 188838. 11. Waheed, A. A.; Rao, K. S.; Gupta, P. D. Mechanism of dye binding in the protein assay using eosin dyes. Anal. Biochem. 2000, 287, 73-79. 12. Waheed, A. A.; Gupta, P. D. Application of an eosin B dye method for estimating a wide range of proteins. Wikborg, M. Pre-stained 3,3 0 ,5,5 0tetrame-thylbenzidine substrates for the detection of enzyme activity. PCT Int. Appl. WO 9904261, 1999; Chem. Abstr. 1999, 130, 150342. 15. Sumiya, M. Dyeing of substrates. Jpn. Kokai Tokkyo Koho JP 62021884, 1987; Chem. Abstr. 1987, 107, 117243. 16. Moeller, H.; Meinigke, B. Hair dye containing nitroxanthene derivatives. Eur. Pat. Appl. EP 1199065, 2002; Chem. Abstr. 2002, 136, 345464. 17. Massimine, K. M.; McIntosh, M. T.; Doan, L. T.; Atreya, C. E.; Gromer, S.; Sirawaraporn, W.; Elliott, D. A.; Joiner, K. A.; Schirmer, R. H.; Anderson, K. S. Eosin B as a novel antimalarial agent for drugresistant Plasmodium falciparum. Antimicrob. Agents Chemother. 2006, 50, 3132-3141. 18. Das Gupta, P.; Waheed, A. L. A.; A process for the preparation of a formulation useful for the detection and estimation of proteins present in biological fluids. Zimmermann, H.; Fritz-Wolf, K. Ellagic acid-related compound and polyaromatic phenol inhibitors of glutathione-S-transferase, and their therapeutic use. PCT Int.