Label-free monitoring of DNA methyltransferase activity based on terminal deoxynucleotidyl transferase using a thioflavin T probe

•A novel, label-free fluorescence assay has been developed for the detection of Dam methyltransferase (MTase) activity.•This method is highly selective and sensitive with a 0.1 U/mL limit of detection.•Because no labeling was required, the method is simple and low cost.

We have developed a new methodology for fluorescence turn-on detection of DNA methyltransferase (MTase) activity based on terminal deoxynucleotidyl transferase (TdT) using a thioflavin T probe. This method is highly selective and sensitive. The fluorescence intensity was direct proportion to Dam MTase concentration in the range from 0.1 to 8.0 U/mL with a detection limit of 0.1 U/mL. And because no labeling with a fluorophore–quencher pair was required, it is simple and low cost. We envision that our novel fluorescent detection method for Dam MTase activity could be applied as a useful tool in biomedical research.