FIG. 3.
Dependence of hybrid stability on the relatedness of the probe sequence to the target sequence. The Tm of the hybrids formed by each of the four sloppy molecular beacon probes with 27 different species-specific oligonucleotide targets is plotted as a function of the number of mismatched base pairs in the hybrid. In general, the more mismatches present, the lower the Tm. Since each of the four molecular beacons possessed a different probe sequence, the set of four Tm values obtained for a particular species-specific target serves as a unique signature that identifies the species that is present. Results for M. chubuense (red), M. malmoense (blue), and M. triviale (orange) provide examples of unique species-specific signatures.