8-Aminoquinoline-based ratiometric zinc probe: Unexpected binding mode and its application in living cells

PMQA, an 8-aminoquinoline-based ratiometric fluorescent sensor, demonstrates the Zn2+-induced red-shift of emission (85 nm), and was successfully applied to image zinc in living cells. Compared to 2:1 stoichiometry in PMQA-Zn2+, PMQA-Cu2+ shows 1:1 composition. Both nitrogen atoms from the aminoquinoline are missing in binding of zinc, while they are critically involved in Cu2+ chelation. The structure difference between PMQA-Zn2+ and PMQA-Cu2+ might shed light in designing novel zinc probes without suffering from copper interference.