Two dansyl fluorophores bearing amino acid for monitoring Hg2+ in aqueous solution and live cells

A series of compounds (1–4) bearing one or two dansyl fluorophore(s) based on a Lys amino acid were synthesized in solid phase synthesis. Among them, two dansyl labeled Lys amino acid 3 detected Hg2+ in a 100% aqueous solution with high sensitivity (Kd=4.3 nM) via a turn-on response. Compound 3 was applied for monitoring Hg2+ in environmental and biological fields. 3 showed a hypersensitive response to Hg2+ without interferences from other metal ions and satisfied the requirements for monitoring the maximum allowable level (2 ppb) of mercury ions in drinking water demanded by EPA. In addition, 3 penetrated living HeLa cells and detected intracellular Hg2+. The organic spectroscopic data revealed the two sulfonamide and amide groups of 3 played a key role in stabilizing the 3-Hg2+ complex.