Figure 4.

Mechanical rupture a triplex by breaking reverse Hoogsteen pairs between a TFOs and its targeting dsDNA using rescue-rope strategy. (A) The GA TFOs binds its targeting Watson–Crick (|) duplex by reverse Hoogsteen pairing (*), forming an antiparallel triplex regarding the purine strand. Mechanical manipulation indicated by arrows can directly disturb reverse Hoogsteen pairs in the triplex. (B) Force-extension curves from a single molecule showed rupture events, indicating the dissociation of the GA TFOs from a triplex structure. Smooth red lines represent the fit of a WLC model. Force-ramp assays were performed at room temperature of 23°C in a buffer containing 10 mM of Tris (pH 7.5), 30 mM of NaCl and 10 mM of MgCl₂. (C–E). Distributions of extension (C) and force (D) as well as the plot of force versus extension (E). The solid blue line in (E) was estimated from a WLC model with parameters from (B). Same buffer and temperature conditions as that in (B).