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Chemical Sciences
Lead Detector Uses DNA
Exposure to lead in the environment has been linked to mental retardation in children. Amounts as small as 0.1 milligrams per liter can impair neurological development, contributing to hyperactivity, learning disabilities, and hearing problems.
A new lead detection method developed by Yi Lu, a professor of chemistry, and graduate student Jing Li may help prevent these impairments by providing a portable, inexpensive, and highly accurate alternative for detecting lead in the environment. Tests run in their lab, and published in October in the Journal of the American Chemical Society, have detected the metal at concentrations 50 times below levels considered dangerous.
Existing methods rely on expensive lab-based analyses to detect lead in suspect samples of paint or soil. Lu's method employs sequences of DNA—the genetic material found in living cells—that have been modified to glow in the presence of lead. In its natural state, DNA is fluorescent. Lu and Li developed a way of attaching a strand of DNA to a "quencher" compound that prevents it from fluorescing unless exposed to lead, which cleaves the bond between the two. The higher the concentration of lead, the more the DNA glows. The sensor is highly selective for lead, enabling it to be detected even in the presence of other metal ions. A similar process, using different sequences of DNA, may also work in detecting contamination by other metal ions, such as mercury.
Lu is patenting his process, which he hopes to see in portable sensors within five to ten years.
Winter 2001