71418-44-5

Bromobimanes in solution (aqueous or organic solvents of medium polarity) react with small thiols [e.g., the tripeptide thiol glutathione (GSH)], and with reactive protein thiol groups (e.g., hemoglobin). The reactions of bromobimanes with thiols are second order and dependent on pH, the active nucleophile being the thiolate anion. The reaction of bromobimane with a thiolate converts the nonfluorescent agent into water-soluble fluorescent products. The neutral agents mBBr and bBBr are moderately soluble in mediumpolarity organic solvents (acetonitrile, dichloromethane), and slightly soluble in water. The quaternary salt, qBBr, and the anionic bromobimane, SBBr, are soluble in water, but less soluble in organic solvents. Bromobimanes are yellow. The highly selective, rapid reactivity of bromobimanes toward thiols, the stability and fluorescence yield of the thiol derivatives, the ease of separation of the derivatives by reversed-phase HPLC, and the availability of both cell-penetrating and nonpenetrating forms, make the use bromobimanes an extremely powerful approach to the analysis of low molecular weight biothiols.