A new fluorescent metal sensor with two binding moieties

A new fluorescent chelator Oxa, having two metal-binding sites, was designed and synthesized in six steps. Oxa exhibited two distinctive dissociation constants for Zn2+ ( K d 1 = 1.50 μM and K d 2 = 140 μM), with considerable fluorescence increase in aqueous buffer at pH 7.2. Affinities of Oxa for the other biologically important ions such as Ca2+ ( K d 1 = 250 μM and K d 2 = 275 mM) and Mg2+ ( K d 1 = 975 μM and K d 2 could not be determined) in the same conditions were also obtained.