"You can imagine that in the computer industry, you want to make better and better computers," Qian says. "This is our effort to do the same. We want to make better and better biochemical circuits that can do more sophisticated tasks, driving molecular devices to act on their environment."
To build their circuits, the researchers used pieces of DNA to make so-called logic gatesdevices that produce on-off output signals in response to on-off input signals. Logic gates are the building blocks of the digital logic circuits that allow a computer to perform the right actions at the right time. In a conventional computer, logic gates are made with electronic transistors, which are wired together to form circuits on a silicon chip. Biochemical circuits, however, consist of molecules floating in a test tube of salt water. Instead of depending on electrons flowing in and out of transistors, DNA-based logic gates receive and produce molecules as signals. The molecular signals travel from one specific gate to another, connecting the circuit as if they were wires.
Winfree and his colleagues first built such a biochemical circuit in 2006. In this work, DNA signal molecules connected several DNA logic gates to each other, forming what's called a multilayered circuit. But this earlier circuit consisted of only 12 different DNA molecules, and the circuit slowed down by a few orders of magnitude when expanded from a single logic gate to a five-layered circuit. In their new design, Qian and Winfree have engineered logic gates that are simpler and more reliable, allowing them to make circuits at least five times larger.'/>"/>
|Contact: Deborah Williams-Hedges|
California Institute of Technology