Credit: © 2009 NPG

Although it is more commonly referred to as the building block of life, DNA is also a useful construction material for building well-defined geometric structures at very small scales. Clever combinations of DNA strands with sequences that are designed to 'instruct' the assembly of a particular object have been used to make molecular architectures including octahedrons, cubes, ladders and two-dimensional periodic arrays.

Now, a team led by Ned Seeman from New York University and Chengde Mao from Purdue University have added an extra dimension1 to the practice of DNA construction. By making a triangular building block from three DNA double helices whose axes all lie in different planes, they have been able to produce periodic assemblies that extended in three dimensions rather than two — resulting in the formation of macroscopic DNA crystals. The individual DNA triangles recognize one another and assemble into larger structures because of the overhanging single strands — so-called sticky ends — at the ends of each of the three helices from which they are made.

It is suggested that these rigid DNA lattices could prove useful for a number of applications, in which they would act as a scaffold to direct the assembly of other components. In particular, they could be used to organize other biological macromolecules for crystallographic analysis, or serve as templates for nanomechanical or nanoelectronic devices.