DNA computer used Google-like logic for math, scientists say

The most complex DNA computer ever developed used the logic functions “and,” “or,” and “not” to solve math problems, the same process applied by mechanical computers, researchers reported in the journal Science.

Introducing computation into a biological cell may provide new ways to seek out disease using similar logic and terminology as Google Inc.’s search engine, or lead to more-efficient drug testing, said Leonard Adleman, a professor of computer science and molecular biology at the University of Southern California in Los Angeles who wasn’t involved with the work.

The calculations were done using 74 strands of DNA that scientists manipulated into gates that control the movement of molecules, depending on which logic function is needed. It is the largest such “computer” ever developed, said researchers at the California Institute of Technology. They used it to find square roots for numbers up to and including 15, and said future uses are yet to be determined.

“What’s impressive is its sophistication and scale,” said Adelman, the first researcher to use strands of DNA for this purpose in 1994. “This is a greater and greater mastery over the molecular level.”

One problem with biological systems is that some molecules don’t clearly signal “on” and “off,” the positions necessary to make a circuit work. The computer constructed by the scientists amplified some signals and silenced others to clarify the signaling process, said Erik Winfree, a professor of computer science and bioengineering at the Pasadena institute who helped develop the computer.

“There are many potential applications,” Winfree said. “People built a PC and didn’t know what they’d be good for. Then programs like spreadsheets and word processors came around, and the builders were surprised by these applications we now don’t know how to live without.”

One eventual use for DNA computers, Winfree said, may be to organize molecules in a beaker to help develop new drugs.

“Man’s been doing chemistry for thousands of years, and nature’s been doing chemistry for millions,” Adleman said. “The gulf between the laboratory and life is for the first time being crossed, and these results are an important step along this journey. We’re crossing the gulf.”