Filling a test tube with molecules made from folded DNA can work as a simple computer. The approach has been used to split two numbers into prime factors.
Conventional computers work by passing electricity through tiny on-off switches to perform simple calculations. However, the new computer relies on the way that differently shaped DNA molecules combine.
Yinan Zhang at Shanghai Jiao Tong University in China and his colleagues used a process called DNA origami, where chemicals contort, intertwine and stick together long strands of DNA. They used this to make DNA structures shaped like rectangular tiles, some of which were hollow in the middle.
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The edges of these shapes all had unique chemical properties, so the researchers considered each one as encoding a different number. When two different edges stuck together through a chemical reaction this was equivalent to a mathematical operation.
To make the computer, the researchers mixed many different shapes in a test tube and incubated it to let them all react with each other. Each reaction produced differently shaped molecules, so the result of the computer鈥檚 calculations could be determined by counting these shapes.
The researchers designed the molecules to give the computer a way to combine the numbers 2 and 3 when they wanted to split 6 into primes, and 2, 3, 5 and 7 when they wanted to split 15. They let the computer run for 4 hours or until all reactions had stopped. The predominant molecule shapes that were produced corresponded to the product the computer settled on as correct.
For factoring 6, for instance, about 63 per cent of the molecules ended up in the shape that could only be made through reactions corresponding to 2 times 3, while approximately 4 per cent assumed shapes that would point to 2 times 2.
鈥淔ifteen years ago, I developed some theory for how to use DNA molecules assembling into shapes to factor numbers, but my colleagues and I were nowhere near being able to do it in an experiment,鈥� says聽 at University of Massachusetts Amherst, who wasn鈥檛 involved with the experiment. 鈥淭his team is now factoring very small numbers, but it is exciting to see that it can work.鈥�
Encoding information is a key function of DNA, and one small beaker of the genetic material could contain as much information as a supercomputer. Since the 1990s, researchers have been trying to leverage these advantages to make DNA computers that would be powerful and could be mixed in the lab instead of wired together in factories. But, they have had limited success. Brun says that their biggest potential may be in medicine where they could work inside of living cells.
鈥淚 can imagine building a DNA computer that goes inside a cell and does some computation based on which proteins are present, like to determine whether the cell is infected by cancer. And then it could decode to release a drug to kill just that cell, targeting it very specifically,鈥� he says.
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