Molecular Beacons
A molecular beacon is a single-strand oligonucleotide hybridization probe forming a stem-and-loop structure. The loop in this sequence is complementary to a target sequence on a larger nucleotide structure (DNA or RNA) and thus works as a probe, and the stem is formed by annealing the complementary arm sequences on either side of the loop.
Molecular beacons do not fluorescence when free in solution, but when they are bonded to a target sequence, they undergo changes, primarily a separation of the stem sequences, that cause them to fluoresce brightly. This means that if the probe does not find a target, the molecular beacon will not glow.
The bonding process is similar to taking a hairpin and separating the legs, with the loop bonded to the target sequence. The separation of the stem pulls a fluorophore and quencher away from one another, enabling the fluorophore to fluoresce.
Molecular beacons have a variety of probe applications in molecular biology. In gene amplification, for instance, molecular targets planted in the genes can give scientists information on how many genes have been produced. And since molecular beasons can be synthesized to produce differently colored fluorophores, a lot of complex information can be gained from their fluorescing. Their high specificity (down to a single nucleotide) makes them valuable in genetic screening.
Web Resources On Molecular Beacons
PHRI: Molecular Beacons
Molecular Beacon Introduction
Book Resources On Molecular BeaconsDNA Microarrays: A Molecular Cloning Manual by David Bowtell et al
Principles of Molecular Pathology by Anthony A. Killeen
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