Time trajectories of enzyme activities with flow-stretching bead assay. (A) Helicaese unwinds duplex DNA (dsDNA → ssDNA). Slope in time trajectory is the unwinding rate. Helicase dissociation drives reannealing of unwound strands (ssDNA → dsDNA). (B) The primer extension of DNA polymerases (ssDNA → dsDNA). (C) The strand excision by exonuclease (dsDNA → ssDNA).