Figure 1: Helicase unwinding through a cis-syn CPD lesion.

The two single-stranded ends of a dsDNA were held at a constant unzipping force of 6–12 pN as T7 helicase unwound the dsDNA. A CPD lesion (red star) was located in either the leading- (a) or lagging- (b) strand DNA. Representative traces show the number of unwound base pairs versus time in the presence of 2-mM Thymidine triphosphate (dTTP). For clarity, traces have been shifted along the time axis. The dotted lines indicate the lesion position.