DNA computers take shape
10th Jan 2000
Anchoring DNA to a substrate may liberate its computing potential.
Scientists have made a small but vital step forward in the quest to
harness the vast computing potential of DNA.
The US team show that DNA computing can be simplified by attaching
the molecules to a surface and then be used to tackle real and complex
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
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
"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 gramme 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 nonconventional
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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