Modular and tunable chemosensor scaffold for divalent zinc

A modular peptide scaffold has been developed for fluorescent sensing of divalent zinc. The signaling component of the chemosensor is the chelation -sensitive fluorophore 8-hydroxy-5-(N,N-dimethylsulfonamido)-2-methylquinoline, which is prepared as the protected amino acid derivative Fmoc-Sox-OH and integrated into peptide sequences. Nineteen synthetic peptides incorporating the signaling element exhibit a range of affinities for Zn2+ through variation of the type and number of Zn2+ ligands, ligand arrangement and the beta-turn sequence that acts as a preorganization element between the ligands. The stoichiometry of the peptide-Zn2+ complexes is evaluated by several criteria. The fluorescence response of these peptides to pH and various important metal ions is reported. Eleven of these sequences form only 1:1 complexes with Zn2+ and their affinities range from 10 nM to nearly 1 muM. When used in concert, these sensors can provide Zn2+ concentration information in a valuable range.