Photoelectrochemical identification of 5-methylcytosine modification in DNA: combination of photosensitization and enzymatic cleavage.

We present a novel photoelectrochemical approach for discriminating between cytosine and 5-methylcytosine in DNA when used in combination with enzymatic digestion. A photosensitizer-linked DNA duplex bearing 5-methylcytosine or cytosine at a given restriction site of the strand was immobilized on a gold electrode and digested with enzyme, and the photocurrent response was measured. We observed high photocurrent density that was selective for the methylated duplex.