Last author

DNA molecules can be folded to create arbitrary two-dimensional shapes, such as smiley faces and stars (P. W. K. Rothemund Nature 440, 297–302; 2006). This pioneering discovery by Paul Rothemund has inspired many, among them Jørgen Kjems, a molecular biologist at Aarhus University in Denmark. He and his colleagues set out to see whether they could translate Rothemund's 'DNA origami' into three dimensions (see page 73). Kjems tells Nature about prompting DNA molecules to self-assemble into a hollow, nanometre-scale box.

How did you get DNA molecules to form a box shape?

All single-stranded DNA molecules can self-assemble, or direct themselves into a particular structural configuration. We first used a computer program to predict what sequences to synthesize that would direct the molecules to assemble into this structure. Then, we used one long, naturally occurring molecule from a virus, and about 220 short artificially synthesized molecules that bound to the long molecule to build a box 42 by 36 by 36 nanometres. This method can be used to assemble any shape — our DNA box is just the beginning.

Can you put anything into the box?

It may be possible to put an enzyme into the box that produces a signal only when the lid is open and the substrate becomes available. The box could effectively become a sensor to signal the presence of a gene from a virus or a bacterium, for example. We are also experimenting with hiding a drug in the box that can kill a cell when the box opens. And we think that the box could potentially be used to make simple arithmetic calculations. Thus, if you have many boxes, you can make very complicated calculations — or effectively create a DNA computer.

Were there surprises along the way?

What surprised me is that nature can direct self-assembly so nicely. I still don't understand how the process actually works. The biggest struggle we faced was working with the DNA itself. DNA isn't very stable because it is easily degraded by enzymes, which tear it into pieces. We're working on trying to use unnatural building blocks, by chemically altering the nucleotides that make up DNA, to make these structures more stable.

Is this a popular field?

Yes. We just managed to be the first group to publish a complex three-dimensional DNA structure — there is a wave of similar experiments going on worldwide. This is intriguing enough that you'd say, 'let's try it.'