Folding DNA into Twisted and Curved Nanoscale Shapes

Stressful Self-Assembly One way to control shape during the assembly of an object is to design in stresses that cause a planned amount of deformation. Dietz et al. (p. 725; see the Perspective by Liu and Yan) designed DNA helix bundles, arranged in honeycomb lattices, in which some of the helices have insertions or deletions relative to the other helices in the bundles. The stresses help the bundles assemble into objects on the scale of tens of nanometers. Both the direction and degree of bending could be controlled, and curvatures as tight as 6 nanometers achieved. Complex shapes, such as square-toothed gears, could be created by combining multiple curved elements. Site-directed insertions and deletions of base pairs direct twist and curvature in crystal-like DNA arrays. We demonstrate the ability to engineer complex shapes that twist and curve at the nanoscale from DNA. Through programmable self-assembly, strands of DNA are directed to form a custom-shaped bundle of tightly cross-linked double helices, arrayed in parallel to their helical axes. Targeted insertions and deletions of base pairs cause the DNA bundles to develop twist of either handedness or to curve. The degree of curvature could be quantitatively controlled, and a radius of curvature as tight as 6 nanometers was achieved. We also combined multiple curved elements to build several different types of intricate nanostructures, such as a wireframe beach ball or square-toothed gears.