Construction of a Turn Off-On-Off Fluorescent System Based on Competitive Coordination of Cu²⁺ between 6,7-Dihydroxycoumarin and Pyrophosphate Ion for Sensitive Assay of Pyrophosphatase Activity

Figure 3

(a) Fluorescence changes of DHC (500 μM) in the absence (curve A) and the presence of various cations (curves B to O) in HEPES buffer aqueous solution (10 mM, pH 6.5). (b) Fluorescence responses of DHC (500 μM) at 475 nm in the absence (black bars) and presence of different cations (1 to 15: Cu²⁺, Fe³⁺, Fe²⁺, Zn²⁺, and Al³⁺ 200 μM; Cr³⁺, Pb²⁺, Ni²⁺, Cd³⁺, Co²⁺, and Ag⁺, 100 μM; Na⁺, K⁺, Mg²⁺, and Ca²⁺, 500 μM) (red bars). Other reaction conditions are the same as Figure 1.

(a)

(b)