A new computer can perform a billion computations per second. That's still much slower than the best silicon computers, but not bad for a soup of DNA and enzymes. The first fully automated DNA computer, it could lead to breakneck acceleration of DNA screening in the next few years.
Previous DNA computers have needed a little prodding from researchers, such as changing the temperature or adding chemicals along the way, says Ehud Shapiro of the Weizmann Institute of Science in Rehovot, Israel, an author of the current study in the 22 November issue of Nature. His team's carefully crafted melange of DNA and enzymes, however, allows the new computer to run without human intervention.
The machine's "hardware" consists of restriction enzymes, which cleave specific sequences of DNA at specific points. To ensure that the enzymes cut correctly, eight kinds of DNA fragments--the "software"--take turns attaching to the DNA that's added as input data. To assemble the machine, the researchers mix trillions of both enzyme and DNA molecules together with water. Once the computer finishes reading and cutting the input DNA, a specific detector DNA molecule in the solution latches on, and the researchers determine the result by electrophoresis.
The group has so far managed to process just 24 base pairs at a time--the input data added to the solution--and only on artificial DNA. But future upgrades may make it possible for the computer to directly analyze collections of real DNA (for example, determining which version of a gene is included in a certain sequence), or even roam the human blood stream seeking out disease and releasing the appropriate drugs, Shapiro says.
"The idea is very smart. It involves only very simple reactions, but it is powerful enough to implement any finite automaton," says Masami Hagiya, a computer scientist at the University of Tokyo who helped create a nearly automated DNA computer last year (ScienceNOW, 18 May 2000). But in case the thought of molecular automatons coursing through your veins is troubling, Shapiro offers the reassurance that such technology is "decades" away.