Single-mismatch detection using nucleic acid molecular 'light switch'

A novel nucleic acid molecular ‘light switch’ method is developed for the sensitive recognition and detection of a single-base mismatched oligonucleotides. The detection limit of oligonucleotide of perfect double stranded and that with single-base, two-base and three-base mismatched are 0.11, 0.17, 0.34 and 1.5 ng ml⁻¹, respectively. It was found that Ru(phen)₂(dppx)²⁺ (phen=1,10-phenanthroline, dppx=7,8-dimethyl-dipyridophenazine) can be used to detect and recognize the perfect double stranded oligonucleotides from mismatched and random targets by the intensity of fluorescence and temperature. This method can be used to recognize and quantitatively detect target DNA with specific sequence. The advantage of this method is that no requisites are needed to separate the coexisting random targets in the case of a mixed solution containing perfect, mismatched and random targets, which make the recognition analysis of oligonucleotide simple and fast. Moreover, it has potential in the study of dynamic process of DNA hybridization.