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 1

(a) Schematic illustration of the turn off-on-off fluorescent strategy based on competitive coordination of Cu²⁺ between DHC and PPi for PPase activity assay. (b) Fluorescence spectra of the mixtures prepared by separate addition of 500 μM DHC; 500 μM DHC and 200 μM Cu²⁺; 500 μM DHC and 200 μM Cu²⁺ and 200 μM PPi; 500 μM DHC and 200 μM Cu²⁺ and 200 μM PPi and 0.25 U PPase. Buffer, HEPES buffer aqueous solution (10 mM, pH 6.5); the reaction temperature, 25°C; cuvette width: 1 mm.  nm.

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