Molecular beacons are single-stranded oligonucleotide hybridization probes that form a stem-and-loop structure. The loop contains a probe sequence that is complementary to a target sequence, and the stem is formed by the annealing of complementary arm sequences that are located on either side of the probe sequence. A fluorophore is covalently linked to the end of one arm and a quencher is covalently linked to the end of the other arm. Molecular beacons do not fluoresce when they are free in solution. However, when they hybridize to a nucleic acid strand containing a target sequence they undergo a conformational change that enables them to fluoresce brightly.
In the absence of targets, the probe is dark, because the stem places the fluorophore so close to the nonfluorescent quencher that they transiently share electrons, eliminating the ability of the fluorophore to fluoresce. When the probe encounters a target molecule, it forms a probe-target hybrid that is longer and more stable than the stem hybrid. The rigidity and length of the probe-target hybrid precludes the simultaneous existence of the stem hybrid. Consequently, the molecular beacon undergoes a spontaneous conformational reorganization that forces the stem hybrid to dissociate and the fluorophore and the quencher to move away from each other, restoring fluorescence.
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Schlachter S, Chan K, Marras SAE, and Parveen N (2017) Detection and differentiation of lyme spirochetes and other tick-borne pathogens from blood using real-time PCR with molecular beacons. Methods in Molecular Biology 1616: 155-170.
Catrina IE, Bayer LV, Yanez G, McLaughlin JM, Malaczek K, Bagaeva E, Marras SAE, and Bratu DP (2016) The temporally controlled expression of Drongo, the fruit fly homolog of AGFG1, is achieved in female germline cells via P-bodies and its localization requires functional Rab11. RNA Biol 13: 1117-1132.
Vargas DY, Kramer FR, Tyagi S, and Marras SAE. (2016) Multiplex real-time PCR assays that measure the abundance of extremely rare mutations associated with cancer. PLoS ONE 11, e0156546.
We describe the use of “SuperSelective” primers that enable the detection and quantitation of somatic mutations whose presence relates to cancer diagnosis, prognosis, and therapy, in real-time multiplex PCR assays that can potentially analyze rare DNA fragments present in blood samples (liquid biopsies), thereby providing information that can be used to modify therapy for individual patients, prolonging (and improving the quality of) life.
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