Figure 2.

Schematic of the DX signal-passing tile structures. Each tile shares the same core strand sequence (cyan). a) Tile A is the initiator of the assembly signal cascade, while tiles B, C, D, and E each have the complete signaling machinery with a signal strand on the upper right tethered by a poly-T sequence. The upper right of each DX tile has a cover strand (colored purple) that protects the output strand from hybridizing until it has been removed by the signal strand when the signal strand is displaced by a binding event on the input end of the tile. b) Tiles B and D have a 5’ input sticky end and 3’ output sticky end, while these strand polarity orientations are reversed for Tiles C and E in panel c). The lower helix plays a passive role and has 2-nucleotide sticky ends designed to facilitate orientation of the DX tiles, but these interactions are not strong enough to form base pairs at ambient temperatures and concentrations.