DNA-based chemical computer calculates square roots
DNA computing was first proposed in the mid-90s and uses chemical reactions to solve problems, using DNA strands as ‘bits’. The work recently published in Science by Lulu Qian and Erik Winfree from Caltech demonstrates the use of DNA for performing calculations (ie, finding the square roots of numbers up to 15). Made from 130 DNA strands, the systems uses logic gates (the OR, AND, etc. functions) that are made of carefully selected DNA sequences; the input and ouptut signals are also DNA strands.
When input strands are added to a mixture containing the sophisticated DNA system, cascade reactions between the DNA strands are initiated, that sequencially zip and unzip from one another depending on the inputs. After the computation has been performed (ie, the cascade reactions stop), the response appears under the form of a given fluorescence colour. For each output, a specific colour indicates ‘0′, and another colour corresponds to ‘1′ (like ‘real’ computers, this one works in binary numbers). The researchers used the ’square root solving problem’ to demonstrate the capacities of their system. However, one of the remarkable points of the piece of work is its very systematic design: one can therefore imagine different function for such a system, like diagnosing illnesses: such a device could provide specific responses depending of what chemicals are present in a patient’s blood, for example.
