A "turn-on" fluorescent chemosensor based on peptidase for detecting copper(II).

A new fluorescent chemosensor for Cu(II) ions was designed and synthesized on the basis of the sequence-specific cleavage of the peptide bond by the peptidase (metal or metal complexes). In the chemosensor system, the substrate was labeled with a FAM fluorophore (6-carboxyfluorescein) at the N-terminal and with a Dabcyl quencher 4-(4'-dimethylaminophenylazo)benzoic acid at the ε-N of C-terminal Lys. In the presence of Cu(II), the substrate strand is cleaved, and the release of the cleaved fragment results in a significant fluorescence increase. The design was aided by the FRET study that showed a "turn-on" response for Cu(II) in an aqueous medium. Under optimum conditions, the novel chemosensor described here had a linear response range for Cu(II) from 1.0 × 10(-8) to 1.0 × 10(-6) mol dm(-3) with a detection limit of 1.0 × 10(-8) mol dm(-3).