Significant enhancement of fluorescence on hybridization of a molecular beacon to a target DNA in the presence of a site-specific DNA nickase.

We have developed a simple isothermal (55 degrees C) reaction that permits detection of DNA targets using only two components: a molecular beacon and a site-specific DNA nickase without deoxyribonucleotide triphosphates and primers. The loop sequence of the molecular beacon should contain a DNA nickase recognition site. The nickase-molecular beacon (NMB) combination permits a 100-fold increase in fluorescent signal. The applications of the NMB assay for enhancement of fluorescent signal in some isothermal methods are discussed.