Figure 4.

(a) Fluorescence enhancement rate as a function of UO₂²⁺ concentration (0∼60 nM) for ATMND/39S_va/39E_va. Inset: 0∼1 μM UO₂²⁺ range. (b) Selectivity of ATMND/39S_va/39E_va toward UO₂²⁺ over other metal ions. 1∼16: 500 nM UO₂²⁺, 125 nM UO₂²⁺, 2 μM Mg²⁺/Ca²⁺/Sr²⁺/Ba²⁺, Mn²⁺, Fe²⁺, VO²⁺, Th⁴⁺, Tb³⁺, Eu³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺, Hg²⁺. Condition: 50 mM MES pH 5.5 and 300 mM NaCl at 5 °C. λ_ex/λ_em = 358/405 nm.