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Fast and reliable assessment of minute amounts of molecular compounds from blood serum samples represents the basis for diagnosis of many diseases. Commonly, heterogeneous assay formats like the enzyme linked immunosorbant assay (ELISA) or western blot are used to detect minute quantities of analyte molecules from serum samples. However, these assay formats suffer from time-consuming assay protocols due to several washing and incubation steps, as well as possible false-positive signals caused by unspecific surface interactions. We focus on the development of fluorescence-based molecular probes for the detection of DNA or antibodies as target molecules directly in homogeneous solution. The fluorescence of oxazine dyes, labeled to flexible peptide-epitope or oligonucleotide sequences, gets quenched selectively upon contact formation with the amino acid tryptophan or the nucleobase guanine. Upon target binding (antibody or target DNA) the conformational flexibility of the probe gets constraint, reducing the intramolecular contact rate between dye and quencher, considerably. Hence, a fluorescence intensity increase signals the binding event (the "molecular beacon" principle). In combination with confocal fluorescence microscopy in the far-red spectral range we are able to detect target molecules at the single-molecule level directly in homogeneous solution, even in complex biological samples (e.g. blood serum).
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| 11.02.2010 | 10:15 - 11:45                         D3-203 Idir Yahiatène: Sensitive detection of DNA at the single molecule level |
Angewandte Laserphysik & Laserspektroskopie