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    Researchers: New DNA Test Method Very Promising

    Chemist Guillermo Bazan (above) and graduate student Brent Gaylord have invented a speedy new way to identify DNA.
    A new method for detecting DNA that could transform medical diagnostics has been reported by UCSB researchers. Currently, tests for the presence of DNA--to identify the presence of a bacterium such as anthrax, or a virus, or a specific gene, for instance--require that the DNA be amplified or grown. The researchers combined the use of a light-emitting polymer with peptide nucleic acid (PNA) probes to make a test so sensitive that costly DNA amplification can be reduced, perhaps eliminated.
    The Proceedings of the National Academy of Sciences article, "DNA Detection Using Water-Soluble Conjugated Polymers and Peptide Nucleic Acid Probes," was written by Brent Gaylord, a graduate student in the Materials Department; his adviser, chemist Guillermo Bazan; and physicist Alan Heeger.
    Bazan and his student Gaylord made a water-soluble conjugated polymer that emits blue light when irradiated with ultraviolet light. The method focuses on a small piece of an unidentified DNA strand. The question the test asks is whether or not that small piece is present in the solution.
    In addition to the light-emitting polymer, the other ingredient of the test is peptide nucleic acid. For the testing method, the PNA is tailor-made to come together with whatever DNA is being sought. Attached to the PNA is a small florescent molecule.
    When the PNA-DNA pair, the little light attached to the PNA tail goes on, indicating a positive identification. Gaylord said that he had successfully used the procedure to detect the presence of a DNA sequence characteristic of anthrax.
    "The beauty of this bio-recognition test, compared to what else is being done, is the simplicity," said Bazan, adding that "the light harvesting properties of the polymer mean that we can sense what we are trying to detect at much lower concentrations."
    Gaylord points to the advantages this method affords for detection of infectious agents over today's standard methods: "We have one testing method that enables direct detection of the invader."
    "This method will significantly decrease the cost of diagnostics," said Bazan.
    --Jacquelyn Savani