DNA can be used to detect dangerous metals
strands of dna isolated from a population of trillions of random dna sequences using 'genetic algorithms' can now be used to detect specific metals. The dna sensors, developed by researchers at the University of Illinois in the us , react to the presence of specific metals like mercury and lead, by emitting light into an inexpensive fibre optic lens. Traditional methods of detecting these metals require lengthy batch testing or relatively expensive equipment. "We have created a new class of dna -based biosensors which are highly sensitive detectors of metals," said Yi Lu, professor at the university. Lu's innovation is based on the fact that dna is not just a repository of genetic information but can also catalyse specific chemical reactions.
The discovery began with Jing Li, Lu's student, separating one-quadrillion random dna strands, individual strands that can fold like proteins, rather than maintaining the familiar intertwined double helix structure. A natural selection process then filtered out strands that could only fold around lead. Li obtained dna strands that could detect lead Then Lu engineered a way to attach a fluorophore (a type of chemical, whose electrons reach excited state and fall back to steady state, in the process emitting energy which creates fluorescence) to one end of the dna strand and a 'fluorescence quencher' on the other end. When exposed to light of wavelength 560 nanometre flourophore electrons should usually reach an excited state, but the quencher's proximity keeps the fluorophore from glowing. But the presence of specific metals cleaves the quenching end away from the flourophore, resulting in an easily detectable 400 per cent increase in fluorescence.
But, to deliver a working sensor technology requires attaching the fluorophore end to a chip base designed to have an optical fibre permanently attached to it. Washing the chips would reset the chips for reuse. The technology will help, believes Lu's funding agency, in different public health related tests, including environmental monitoring, wastewater and treatment, industrial process monitoring, clinical toxicology.
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