August 6, 2009

DNA Computers Embrace Logic

A team of scientists has determined a way to make biomolecular computers think more "Ëœlogically'.

Professor Ehud Shapiro of the Weizmann Institute's Biological Chemistry, and Computer Science and Applied Mathematics Departments led the first team to create an autonomous programmable DNA computing device in 2001.

The first microscopic computing device was able to perform tasks such as checking a list of 0s and 1s to show whether or not there was an even number of 1s.

In 2004, a new device was developed, which showed its ability to detect cancer in a test tube while deploying a molecule to destroy it.

Writing in the journal Nature Nanotechnology this week, Shapiro and research students Tom Ran and Shai Kaplan say they have created a program that will allow biomolecular computers to become more logical, or user-friendly.

"Using more sophisticated biochemistry, we were able to implement simple logic programs, which are more akin to the way people program electronic computers," Professor Shapiro told BBC News.

Researchers trained the device to answer a question offered by Aristotle: "ËœAll 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 "ËœIs Socrates Mortal?' correctly.

Researchers took it a step further each time, offering the device more propositions with added rules and facts. Each time, the DNA computing devices were able to come up with a correct answer.

The correct answer was encoded in a flash of green light: Some of the strands had a biological version of a flashlight signal "“ they were equipped with a naturally glowing fluorescent molecule bound to a second protein which keeps the light covered.

"Of course when the examples are simple, as in today's logic program, one can pre-compute the answer with pencil and paper," said Professor Shapiro. "But in principle there is no difference between simple and complex computer programs; they can compute only what they programmed to compute."

"It is important to note that, while bio-molecular computing trails behind electronic computing - in terms of actual computing power, maturity of the technology, and sheer historical progression - at the conceptual level they stand side-by-side, without one being a more 'preferred' embodiment of the ideas of computation," he said.


On the Net: