Fig. 2: Experimental setup and catch bond sequence design.
a Schematic representation of the dual-trap optical tweezers experiment. The hook is attached to bead A, and the fish is attached to bead B via DNA handles of 2633 and 272 bp, respectively. Both handles are attached to the beads by a biotin-streptavidin linkage on the 5′ end of each handle (top inset). Bead B undergoes an oscillatory motion with a dwell period before retraction (bottom inset) to increase the fishing success rate (binding between the hook and the fish). b The construct sequence. A 9-mer polyethylene glycol (PEG) linker attaches the hook to its DNA handle to minimize nonspecific base interactions with the fish and increase flexibility. c Schematic showing the weak and strong pathways. d The expected τF of the selected construct sequence based on our analytical model, showing the overall expected slip-catch-slip behaviour resulting from transitioning from hook unzipping to hook shearing around the intersection of the jaw opening and the hook unzipping τF at Fc = 13.6 pN. The anticipated force-extension curves differ for the weak (e) and strong (f) pathways, as predicted by the extensible worm-like chain model (XWLC). In the weak pathway, we expect a singular low-force rupture event indicative of hook unzipping (e). In the strong pathway, we expect a jaw-opening transition preceding a high-force rupture event corresponding to hook shearing (f).
