Molecular Beacon

Molecular beacons are used in molecular biology for the identification and quantification of specific DNA hybridization probes. They consist of a single-stranded DNA with a stem-loop or hairpin structure at their 3 ' and 5' ends of the tribe belonging to a fluorescent dye and a quencher. The loop, however, includes a target DNA complementary to the DNA sequence. Hybridization with the target DNA results in a increase in fluorescence, which is used for example, in analytical and Hybridisationsanalysen in quantitative real-time PCR.

Structure

Molecular beacons are typically from 25 to 40 nucleotides and have a stem-loop structure. The mutually complementary and consisting of 5 to 8 base pairs of the 3'- and 5'- ends of the mold base. The loop consists of a 15 to 35 base pairs long, complementary to the target DNA nucleic acid sequence. The 3'-and 5' - ends, are usually coupled to a fluorescent dye and a quencher Dabcyl. The use of a second fluorescent dye instead of the quencher is possible but not in use.

Function

In the unhybridized state at room temperature molecular beacons are in their stem-loop structure. In this case, the fluorescence of the fluorescent dye ( the donor ) is suppressed by a based on the Förster resonance energy transfer energy transfer to the quencher (acceptor). Hybridization of molecular beacons with the target DNA can cause dissolution of their tertiary structures. An increase in donor fluorescence after excitation can be observed by a decrease in the energy transfer as a result of hybridization of molecular beacons with the target DNA.