DNA methylation analysis using metal complex formation

Analysis of the cytosine methylation status of a gene is very important for understanding the expression mechanism of genetic information. However, to distinguish 5-methylcytosine (M) from C, i.e., to detect the existence of only one methyl group in a long DNA strand, is not easy. A rapid and selective chemical reaction capable of distinguishing between M and C would become a useful method for efficiently analyzing the status of cytosine methylation at a specific site in a gene. We herein report M-selective oxidation. M was oxidized efficiently by exposure to a reaction mixture containing an osmium complex, making possible a clear distinction from very weak oxidation of C. We readily obtained information on the methylation status at a specific site by means of M-selective oxidation using functional bipyridine ligands.