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 8

(a) Kinetic plots of time-dependent fluorescence responses versus different activities of PPase present. (b) Fluorescence responses of DHC (500 μM) (curve A) and Cu²⁺-PPi (Cu²⁺: 200 μM, PPi: 200 μM) complex with DHC (500 μM) were recorded at a time point of 30 min after the addition of PPase (curves B to M: 0, 0.1, 0.12, 0.15, 0.17, 0.2, 0.22, 0.25, 0.27, 0.3, 0.35, and 0.4 U) in HEPES aqueous buffer (10 mM, pH 6.5) in the presence of 500 μM Mg²⁺. The final volume of each resulting mixture was adjusted to 500 μL. (c) Fluorescence responses versus . Error bars were estimated from three replicate measurements. Other reaction conditions are the same as Figure 1.

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