DNA computation gets logical at the Weizmann Institute ...( Biomolecular computers made of DNA a...)

Biomolecular computers, made of DNA and other biological molecules, only exist today in a few specialized labs, remote from the regular computer user. Nonetheless, Tom Ran and Shai Kaplan, research students in the lab of Prof. Ehud Shapiro of the Weizmann Institute's Biological Chemistry, and Computer Science and Applied Mathematics Departments have found a way to make these microscopic computing devices 'user friendly,' even while performing complex computations and answering complicated queries.

Shapiro and his team at Weizmann introduced the first autonomous programmable DNA computing device in 2001. So small that a trillion fit in a drop of water, that device was able to perform such simple calculations as checking a list of 0s and 1s to determine if there was an even number of 1s. A newer version of the device, created in 2004, detected cancer in a test tube and released a molecule to destroy it. Besides the tantalizing possibility that such biology-based devices could one day be injected into the body a sort of 'doctor in a cell' locating disease and preventing its spread biomolecular computers could conceivably perform millions of calculations in parallel.

Now, Shapiro and his team, in a paper published online today in Nature Nanotechnology, have devised an advanced program for biomolecular computers that enables them to 'think' logically. The train of deduction used by this futuristic device is remarkably familiar. It was first proposed by Aristotle over 2000 years ago as a simple ifthen proposition: 'All men are mortal. Socrates is a man. Therefore, Socrates is mortal.' When fed a rule (All men are mortal) and a fact (Socrates is a man), the computer answered the question 'Is Socrates Mortal?' correctly. The team went on to set up more complicated queries involving multiple rules and facts, and the DNA computing devices were able to deduce the correct answers every time.

At the same time, the team created a compiler
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