DNA-friendly Cu(ii)/TEMPO-catalyzed 5-hydroxymethylcytosine-specific oxidation.

The mixture of copper(II) perchlorate and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mildly and specifically oxidized 5-hydroxymethyl-cytosine to yield 5-formylcytosine because of its allyl alcohol specificity. The genomic DNA oxidized at 5-hydroxymethylcytosine by the copper(II)/TEMPO oxidation was efficiently analyzed using various practical methods: DNA cleavage by piperidine, specific functionalization by hydrazone formation, and genome-wide high-resolution microarray.