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 6

(a) Fluorescence changes of DHC (500 μM, curve A) and Cu²⁺-DHC (Cu²⁺: 200 μM, DHC: 500 μM) complex in the absence (curve B) and presence of various anions (curves C to I: Cl⁻, F⁻, Br⁻, I⁻, , , , , , and PPi; 200 μM) in HEPES buffer aqueous solution (10 mM, pH 6.5). (b) Fluorescence responses of DHC (500 μM) (black bars) and Cu²⁺-DHC (Cu²⁺: 200 μM, DHC: 500 μM) complex at 475 nm in the absence (red bars) and presence of different anions (1 to 10: PPi, Cl⁻, F⁻, Br⁻, I⁻, , , , , and ; 200 μM) (blue bars). Other reaction conditions are the same as Figure 1.

(a)

(b)