| Abstract
| - An assay for a target single strand 20-base sequence of DNA coding for the anthrax lethal factor, basedon conjugated polymer fluorescence superquenching, is reported. The assay employs a platform in whichthe receptor (a biotinylated complementary sequence “capture strand”) and polymer (two components: ananionic poly(phenylene ethynylene) (PPE) and a biotinylated −PPE) are co-located on streptavidin-derivatized polystyrene microspheres. A conjugate of the target strand with the energy transfer quencherQSY-7 (DNA-QTL) is used to construct competition assays for the target. A direct competition assaybetween the target-DNA and DNA-QTL for the microsphere-bound capture is only marginally successfuldue evidently to greater kinetic affinity of the polymer-capture ensemble for the conjugate. However asequential addition of target, followed by DNA-QTL affords a quantitative assay for the target by attenuationof PPE fluorescence quenching by the DNA-QTL. Likewise a direct competition in solution between thetarget and DNA-QTL for the biotinylated capture strand followed by addition of microspheres providesa sensitive and quantitative assay for the target single strand DNA.
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