TaqMan

TaqMan probes are hydrolysis probes that are designed to increase the specificity of quantitative PCR. The method was first reported in 1991 by researchers at Cetus Corporation, and the technology was subsequently developed by Roche Molecular Diagnostics for diagnostic assays and by Applied Biosystems (now part of Thermo Fisher Scientific) for research applications.

The TaqMan probe principle relies on the 5´–3´ exonuclease activity of Taq polymerase to cleave a dual-labeled probe during hybridization to the complementary target sequence and fluorophore-based detection. As in other quantitative PCR methods, the resulting fluorescence signal permits quantitative measurements of the accumulation of the product during the exponential stages of the PCR; however, the TaqMan probe significantly increases the specificity of the detection. TaqMan probes were named after the videogame Pac-Man (Taq Polymerase + PacMan = TaqMan) as its mechanism is based on the Pac-Man principle.

TaqMan probes consist of a fluorophore covalently attached to the 5’-end of the oligonucleotide probe and a quencher at the 3’-end (Figure 1). Several different fluorophores (e.g. 6-carboxyfluorescein, acronym: FAM, or tetrachlorofluorescein, acronym: TET) and quenchers (e.g. tetramethylrhodamine, acronym: TAMRA) are available. The quencher molecule quenches the fluorescence emitted by the fluorophore when excited by the cycler’s light source via FRET (Förster Resonance Energy Transfer). As long as the fluorophore and the quencher are in proximity, quenching inhibits any fluorescence signals (Figure 1).

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