Highly efficient incorporation of dATP in terminal transferase polymerization forming the ploy (A)-DITO-1 fluorescent probe sensing terminal transferase and T4 polynucleotide kinase activity.

Fluorescent dye DITO-1 has almost no fluorescence in the absence of nucleic acid. G bases in single strand DNA can induce maximum fluorescent enhancement followed by the A bases when it binds the DITO-1. However, the incorporation efficiency of the dATP was higher than dGTP in terminal transferase (TdT) polymerization. As a consequence, ploy (A), rather than ploy (G) via TdT polymerization had the superior photoluminance when it binded DITO-1 fluorescent dye. Here, we developed a high selective and sensitive sensing strategy for assaying TdT and T4 polynucleotide kinase activity (T4 PNK) based on the ploy (A)-DITO-1 fluorescent probe. An increasing amounts of TdT enzyme could promote the distinct incorporation of dATP on the DNA primer and form poly (A) ssDNA with a difference in length. A good linear relationship between the ΔF and the concentrations of TdT in a range of 0.2-50 U/mL was obtained and the detection limit was 0.05 U/mL. Based on the experimental results for TdT, we further expanded the application of this method for detection of a series of concentrations of T4 PNK. The ΔF and the logarithm concentrations of T4 PNK in the range of 0.1-10 U/mL showed a good linear response and the detection limit of 0.02 U/mL was obtained. In addition, the detection of T4 PNK in Hela cell lysate was achieved, demonstrating that the proposed method had the potential application in complex system. The ploy (A)-DITO-1 fluorescent probe had the excellent properties of one-step readout, robustness for target detection in complex system, and easiness operation, and showed the great potential in clinical diagnostics, inhibitor screening, and drug discovery.