Scorpions^® probes allow Real-Time quantitative PCR and genotyping. They are also suitable for end-point analysis of specific DNA targets. 

Scorpions^® are PCR primers with a “stem-loop” tail containing a fluorophore and a quencher. The “stem-loop” tail is separated from the PCR primer sequence by a “PCR blocker”, a chemical modification that prevents the Taq DNA polymerase from copying the stem-loop sequence of the Scorpions^® primer. Such read-through would lead to non-specific opening of the loop, causing a non-specific fluorescence signal. 

Scorpions^® differ from the specific detection methods discussed so far in that their mechanism of probing is intramolecular. During PCR, Scorpions^® primers are extended to form PCR products. During the annealing phase, the probe sequence in the Scorpion’s tail curls back to hybridize to the target sequence in the newly formed PCR product. As the tail of the Scorpions^® and the PCR product are now part of the same strand, the interaction is intramolecular which is kinetically favorable and highly efficient. Eurogentec proposes three types of Scorpions® probes: Standard Scorpions^®, FRET Scorpions^®, and Duplex Scorpions^®.