Turn-On Fluorescence Sensing of Nucleoside Polyphosphates Using a Xanthene-Based Zn(II) Complex Chemosensor

Fluorescence sensing with small molecular chemosensors is a versatile technique for elucidation of function of various biological substances. We now report a new fluorescent chemosensor for nucleoside polyphosphates such as ATP using metal−anion coordination chemistry. The chemosensor 1−2Zn(II) is comprised of the two sites of 2,2′-dipicolylamine (Dpa)−Zn(II) as the binding motifs and xanthene as a fluorescent sensing unit for nucleoside polyphosphates. The chemosensor 1−2Zn(II) selectively senses nucleoside polyphosphates with a large fluorescence enhancement (F/Fo > 15) and strong binding affinity (Kapp ≈ 1 × 106 M−1), whereas no detectable fluorescence change was induced by monophosphate species and various other anions. The ‘turn-on,’ fluorescence of 1−2Zn(II) is based on a new mechanism, which involves the binding-induced recovery of the conjugated form of the xanthene ring from its nonfluorescent deconjugated state which was formed by an unprecedented nucleophilic attack of zinc-bound water. The selective and highly sensitive ability of 1−2Zn(II) to detect nucleoside polyphosphates enables its bioanalytical applications in fluorescence visualization of ATP particulate stores in living cells, demonstrating the potential utility of 1−2Zn(II).