Movie S1.

Destaining of a YO-PRO-1–stained λ DNA molecule, followed by RecQ-dependent unwinding. Initially, the DNA is fluorescent due to intercalation of the dye molecules. As a solution containing 200 mM NaCl is flowed into the flow cell, the dye dissociates and fluorescence disappears. Subsequently, a solution containing of 80 nM RecQ and AF488SSB is flowed into the flow cell to initiate unwinding; reaction is the same as shown in Fig. 1 B–F. The solution fills the channel 24 s into the movie. The flow, when on, goes from left to right in the movie. The elapsed time is indicated in hours:minutes:seconds. (Scale bar, 5 μm.)