‘Noise’ tunes logic circuit made from virus genes

November 15, 2011

Engineers from Arizona State University in Tempe and the Space and Naval Warfare Systems Center (SPAWAR) in San Diego, Calif., are exploiting noise to control the basic element of a computer: a logic gate, using a genetically engineered system derived from virus DNA.

The scientists focused on a single-gene network in a bacteriophage λ (lamda). The gene they use regulates the production of a particular protein in the virus. Normally, there are biological reactions that regulate the creation and destruction of this protein; upsetting that balance results in a protein concentration that is either too high or too low. The scientists assigned a “1″ to one concentration and a “0″ to the other. By manipulating the protein concentration, the team could encode the logic gate input values and obtain the desired output values.

Researchers modeled the system as two potential energy wells separated by a hump, corresponding to an energy barrier. In the presence of too much noise, the system never relaxes into one of the two wells, making the output unpredictable. Too little noise, on the other hand, does not provide the boost necessary for the system to reach a high enough protein concentration to overcome the energy barrier; in this case, there is also a high probability that the biological logic gate will fail to achieve its predicted computation. But an optimal amount of noise stabilizes the circuit, causing the system to jump into the “correct well” and stay there.

This proof-of-concept work offers the possibility of exploiting noise in biologic circuits instead of regarding it as a laboratory curiosity or a nuisance, the researchers say.

Ref.: Anna Dari, et al., Logical stochastic resonance with correlated internal and external noises in a synthetic biological logic block, Chaos: An Interdisciplinary Journal of Nonlinear Science, 2011; (accepted)