>Scientists Create `DNA Computer'
>Updated 1:22 AM ET January 13, 2000
>By RICK CALLAHAN, Associated Press Writer
>Scientists have created a "DNA computer" from strands of synthetic DNA
>coaxed into solving relatively complex calculations, according to a report
>in today's issue of the journal Nature.
>The short-lived chemical computer has no immediate practical applications,
>but it nudges the fledgling technology of DNA computing further out of
>of science fiction and into the realm of the possible, the University of
>Wisconsin-Madison researchers said.
>"It's kind of a non-automated computer - an abacus of sorts - but it's an
>approach we're confident can be automated like a conventional computer,"
>said Lloyd Smith, a professor of chemistry.
>Conventional computing is driven by computer chips, but that technology is
>fast approaching the limits of miniaturization. Scientists dream of using
>the vast storage capacity that enables DNA and its chemical cousin RNA to
>hold the complex blueprints of living organisms.
>While other researchers have had success with DNA computing, in most of
>those tests the DNA was suspended in liquid-filled test tubes.
>Smith's team, on the other hand, tethered the DNA to a solid surface. That
>simplified the technology, though it remains too rudimentary to be turned
>into large DNA computers capable of tackling problems as complex as those
>solved by conventional computers.
>The Wisconsin researchers coded DNA strands to contain all possible
>solutions to a problem Smith likens to four people each ordering a pizza
>with four combinations of toppings - a problem with 16 possible answers.
>After years of work, his team made several of the computers, each composed
>of about 100 trillion synthetic DNA strands that repeatedly solved the
>problem, though with human help.
>Smith and his colleagues began by arranging the synthetic DNA's genetic
>coding - represented by the letters A, T, C and G - in different
>combinations that represented the numerical solutions to the problem.
>Those DNA strands were fastened to a piece of glass covered with a thin
>sheet of gold, then bathed repeatedly in different solutions of enzymes
>interacted with the DNA to weed out the wrong answers.
>Each "computer" withstood several different calculations over a few days,
>Since DNA computing was first demonstrated in 1994, fewer than a dozen
>research teams have launched molecular computing projects. Together, they
>have a combined budget of only about $1 million, said John Reif, a
>of computer science at Duke University and director of the Consortium of
>"There are multiple ways of using biotechnology to compute. It's not
>predictable which one is best, which one will emerge as the leader just
>isn't clear at this point," Reif said.
>Laura F. Landweber, an assistant professor of biology at Princeton
>University, is leading a team working to exploit RNA's computing
>Her team recently fashioned RNA strands that processed complex problems
>similar to those that chess players encounter.
>While Smith's team produced a chemical computer that tackled a problem
>16 possible solutions, the Princeton RNA computer searched through 512
>possible answers, she said. The research will be published this year in
>journal Proceedings of the National Academy of Sciences.
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