Spectroscopic Study of CpG Alternating DNA-Methylene Blue Interaction for Methylation Detection

Recognition of methylated DNA sites would be useful strategy due to the important roles of methylation in disease occurrence and developmental processes. The interaction of CpG rich methylated and unmethylated DNA hybrid with methylene blue (MB) as an optical probe has been investigated by absorption, emission, circular dichorism and fluorescence anisotropy analysis. Titration of MB with both sequences caused a hypsochromism and decreased the absorption of MB that indicating an intercalative mode of interaction. The experimental results revealed that MB as the optical indicator could distinguish between the methylated and unmethylated DNA sequences. Under optimum conditions, upon the addition of methylated dsDNA, the fluorescence intensity increased in linear range from 1.0 × 10(-9) to 1.0 × 10(-6) M with detection limit of 7.2 × 10(-10) M and on the other hand, the intensity of MB showed no change with addition of unmethylated dsDNA.