After synthesis and mixing of DNA staples and scaffold strands, the structure is able to self-assemble in a single step. The technique has been used to produce remarkable nanostructures of smiley faces, squares, disks, geographic maps, and even words, at a scale of 100 nm or less. But the creation of topological forms capable of reconfiguration, like those produced by nature, has proven more challenging.
Once the tiny Mbius structures had been created, they were examined with atomic force- and transmission electron microscopy. The startling images confirm that the DNA origami process efficiently produced Escher-like Mbius strips measuring less than a thousandth the width of a human hair. Yan notes that the Mbius forms displayed both right and left handed twists. Imaging permitted the handedness or chirality of each flattened nanostructure to be determined, based on the height differences observed at the overlapping areas.
Next, the team demonstrated the topological flexibility of the Mbius forms produced, using a folding and cuttingor DNA Kirigamitechnique. The Mbius can be modified by cutting along the length of the strip at different locations. Cutting a Mbius along its centerline yields a new structurea looped form containing a twist of 720 degrees or 4 half-twists. The design, which the group calls a Kirigami-Ring is no longer a Mbius as it has two edges and two surfaces. The Mbius may also be cut along its length one-third of the way into its width, producing a Kirigami-Catenanea Mbius strip interlinked with a supercoiled ring.
To accurately cut the Mbius nanostructures, a technique known as strand displacement was used, in which the DNA staples holding the central helix in place are outfitted with so-called toe-
|Contact: Joe Caspermeyer|
Arizona State University