Functionalizing Designer DNA Crystals with a Triple-Helical Veneer**

DNA is a very useful molecule for the programmed self-assembly of 2D and 3D nanoscale objects.[1] The design of these structures exploits Watson–Crick hybridization and strand exchange to stitch linear duplexes into finite assemblies.[2–4] The dimensions of these complexes can be increased by over five orders of magnitude through self-assembly of cohesive single-stranded segments (sticky ends).[5,6] Methods that exploit the sequence addressability of DNA nanostructures will enable the programmable positioning of components in 2D and 3D space, offering applications such as the organization of nanoelectronics,[7] the direction of biological cascades,[8] and the structure determination of periodically positioned molecules by X-ray diffraction.[9] To this end we present a macroscopic 3D crystal based on the 3-fold rotationally symmetric tensegrity triangle[3,6] that can be functionalized by a triplex-forming oligonucleotide on each of its helical edges.