DNA Comp… I mean, Nanotechnology

DNA is fascinating to us not merely because it holds information, but because its hybridization to a partner strand means it can recognize information. Release thousands of DNA sequences into a pool, and the simple thermodynamics of hybridization means each strand will end up finding its partner. Thus the dream of DNA computing – massively parallelized by the ability of many, many small pieces to diffuse and hybridize in a solution.

The famous example is the usage of this phenomenon to solve the “travelling salesman” problem , illustrated beautifully by Larry Gonick in Discover Magazine:

Unfortunately, the field of DNA computing dries up a bit after this. It turns out there’s a lot of cross-hybridization of similar sequences, and most computational problems simply can’t be posed in a useful manner in a DNA hybridization context. It’s sad, but the seemingly magical nature of DNA sequence and hybridization just don’t translate into computation the way we’d hope.

The field of DNA computation has morphed, moved on, to the field of DNA nanotechnology. While sequence hybridization can’t scale to practical computation, it can be used to create self-assembling structures. Hence the rather cute (if useless) structure gracing the cover of this week’s Nature…

So here’s some pics. There’s a guy in my lab that works on this stuff, he emailed the article to us and we’ve been ogling the pretty structures woven from DNA, created by Paul Rothemund at Caltech.

It still isn’t useful for anything yet. Well, that guy in my lab, he does have something useful. It’s not published yet. But it’s useful. The funny thing about it is that it’s entirely structural, the specific nature of DNA sequence isn’t used at all. In other words, someone said “we need something of this shape”, and DNA just happens to be material that shape is made of.

It’s a strange change from the fanciful computational nature of DNA sequence to using it as simple material for nanostructures. I think it’s a practical shift of focus. Making little smiley faces does feel like the latest in a long line of useless toy constructs, and a 2D grid limits applications quite a bit, but 3D constructions are possible (if a bit wiggly). Maybe people will realize structures they can use now that the tool exists to make them.

PS – Larry Gonick makes excellent science-based comics. I own his Cartoon History of the Universe. I think his cartoons are awesome.

PPS – I admit, half the reason I’m posting this is because smiley faces made of DNA are so damn cute. Albeit totally useless. :-)

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