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 5

(a) Fluorescence responses of DHC (500 μM) (curve A) and Cu²⁺-DHC (Cu²⁺: 200 μM, DHC: 500 μM) complex with (curves B to F: 0, 10, 30, 50, 100, and 200 μM) in HEPES aqueous buffer (10 mM, pH 6.5). (b) 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: , , , AMP, ADP, ATP, and PPi, 200 μM) in HEPES buffer aqueous solution (10 mM, pH 6.5). Other reaction conditions are the same as Figure 1.

(a)

(b)