Reaction of bisulfite with the 5-hydroxymethyl group in pyrimidines and in phage DNAs

5-Hydroxymethylcytosine reacted with bisulfite and, instead of undergoing usual deamination process, gave cytosine 5-methylenesulfonate as the product. The conversion was rapid and quantitative, and the optimum pH was 4.5. The product was isolated as crystals and characterized. Cytosine 5-methylenesulfonate was only very slowly deaminated by treatment with bisulfite. 5-Hydroxymethyl-2'-deoxycytidine 5'-phosphate reacted with bisulfite in the same way as 5-hydroxymethylcytosine. Residues of 5-hydroxymethylcytosine in native as well as denatured T2 DNA were convertible to those of cytosine 5-methylenesulfonate by treatment of the DNA with bisulfite. While it is known that the 5-hydroxy-methyl groups of T-even bacteriophage DNA can be enzymatically glucosylated, this observation offers chemical evidence that the 5-hydrozymethyl groups in DNA are situated in such a way that they can readily react with external agents. 5-Hydroxymethyluracil gave uracil 5-methylenesulfonate on treatment with bisulfite. This reaction was much slower than that of 5-hydroxymethylcytosine, and the optimum pH was between 6 and 7.