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Wednesday, 12 January, 2000, 19:00 GMT
DNA computers take shape

Anchoring DNA to a substrate may liberate its computing pottential Anchoring DNA to a substrate may liberate its computing pottential

By BBC News Online Science Editor Dr David Whitehouse

Scientists have made a small but vital step forward in the quest to harness the vast computing potential of DNA.

We can see scaling up within a few years by a factor of a trillion or more
Lloyd Smith
The US team show that DNA computing can be simplified by attaching the molecules to a surface and then using them to tackle real and complex problems.

DNA computing is still very much a dream for scientists. They hope to harness the enormous data-storing capacity of DNA, biological molecules that are also able to perform operations similar to a computer's.

DNA can do this through the manufacture of enzymes, which are biological catalysts that could be called the 'software' used to execute the desired calculation.

Simpler and more accessible

The new research, published in the journal Nature, reports the development of novel surface chemistry that greatly simplifies the complex and repetitive steps previously used in rudimentary DNA computers.

It takes DNA out of the test tube and puts it on a solid surface, making the technology simpler, more accessible and more amenable to the development of larger DNA computers.

"It demonstrates DNA computing on surfaces, which provides a relatively simple pathway to upscaling DNA computing to solve large problems," says team leader Lloyd Smith of the University of Wisconsin-Madison.

In the experiments, DNA molecules were applied to a small glass plate overlaid with gold. The DNA was modified so that all the possible answers to a computationally difficult problem were included. By exposing the molecules to certain enzymes, the molecules with the wrong answers were weeded out, leaving only the DNA molecules with the right answers.


The appeal of DNA computing lies in the fact that DNA molecules can store far more information than any existing computer memory chip. It has been estimated that a gram of dried DNA can hold as much information as a trillion CDs.

What is more, in a biochemical reaction taking place in a tiny surface area, hundreds of trillions of DNA molecules can operate in concert, creating a parallel processing system that resembles the processing architecture of the most powerful supercomputer.

The logic behind conventional digital computers represents information as a series of electrical impulses using ones and zeros. DNA computing depends on information represented as a pattern of molecules arranged on a strand of DNA.

Question of scale

Conventional computing, with ever more and smaller features packed onto the silicon chips that power it, is approaching the limits of miniaturisation. Many believe that DNA computing is a way around that barrier.

Current DNA computing technology, Professor Smith emphasises, is still far from overtaking the silicon chip. He says his new method is simply a testbed for working out an improved and simpler chemistry for DNA computing.

Nevertheless, he adds, the new surface chemistry provides an opportunity for harnessing DNA to make the biggest non-conventional computer yet: "We're interested in scale up. We believe that based on the principles we've worked out here, we can see scaling up within a few years by a factor of a trillion or more."

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See also:
23 Jun 99 |  Sci/Tech
Time up for silicon chips
19 Feb 98 |  Sci/Tech
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