Figure 2.

Design of a DNA ring with a stimulus-responsive size. (a) Abstract reaction graph. Each hairpin is represented as a node with three ports, and each key is represented as a node with two ports. Triangles and circles indicate input and output ports, respectively, while their open or filled representation corresponds to an exposed or sequestered toehold. Solid and dashed black arrows indicate assembly and disassembly reactions, respectively. Gray arrows indicate possible reactions that are not used in the designed ring formation. (b) Domain-level strand diagrams. Each unique toehold and branch migration domain is labeled with a distinct letter. Asterisks indicate sequence complementary. The three keys that trigger the self-assembly of DNA rings with four, six, and eight strands are labeled as key4, key6, and key8, respectively.