Eosin-5-isothiocyanate is a good photosensitizer and can be used to selectively label amines. It has a quantum yield of 0.57 for singlet oxygen generation, which makes it useful for photoconversion of electron-rich materials such as diaminobenzidine (DAB) or fluorescent dyes into highly electron-dense materials for high resolution electron microscopy studies. Additionally, eosin is a good fluorescence acceptor for fluorescein (FAM), dansyl and coumarin dyes in fluorescence resonance energy transfer (FRET). &lamba;Ex/&lamba; Em (pH 9) = 521/544 nm ε = 95,000 Orange red solid soluble in DMF or DMSO Store at -20°C and protect from light C21H7Br4NO5S MW: 704.96