Fig. 4: ATP/AzoDiGua aggregates are cation-responsive and valence-selective.
A Scheme of metal ion-triggered ATP/AzoDiGua disassembly by ATP chelation with di- and monovalent cations. B Photographs of ATP/AzoDiGua suspensions before (left) and after (right) addition of different metal cations (MN+) with a ratio [MN+]/[ATP] = 2. C Electron Paramagnetic Resonance (EPR) spectra at T = 110 K of ATP alone (1 mM) (blue solid line), mixture of Cu(NO3)2 (2 mM) and ATP (1 mM) (dashed line), and ATP/AzoDiGua aggregates after disassembly by adding Cu(NO3)2 at a ratio [Cu2+]/[ATP] = 2 (green solid line). D Fluorescence intensity (Exc: 400 nm; Em: 650 nm) of ATP/AzoDiGua suspension after addition of Cu(NO3)2 as a function of the ratio [Cu2+]/[ATP]. The solid line between symbols (data points) is guide for the eye. For all experiments, the initial suspension results from the self-assembly of ATP (1 mM) and AzoDiGua (1 mM) for 10 min. All experiments are done at room temperature in 50 mM Tris HCl buffer solutions (pH = 7.4).
