Signal When You Get There

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Science  15 Jul 2005:
Vol. 309, Issue 5733, pp. 359
DOI: 10.1126/science.309.5733.359b

Quantitating how readily DNA can pass through a thin film is important for designing a gene therapy or drug release system. Measuring permeability accurately requires a method for detecting small amounts of nucleic acid, preferably without the added complication of having to rely on derivatizing the DNA with bulky fluorophores.

Johnston and Caruso have used a molecular beacon approach to monitor the passage of unaltered DNA segments through an organic film that was applied to a mesoporous silica particle with layer-by-layer assembly. Their detector is an encapsulated single-stranded DNA that forms a stem-loop structure and whose ends are labeled with a fluorophore and a quencher. When a complementary DNA molecule passes through the film, it disrupts the stem-loop, freeing the fluorophore to emit a signal. Using this arrangement, they were able to observe the slowing of permeation as the length of the target DNA molecules was increased from 15 to 60 bases. — PDS

J. Am. Chem. Soc. 10.1021/ja0527166 (2005).

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