The effect of sodium bisulfite on the melting profiles of nucleic acids and on their respective nucleosides.

The effect of sodium bisulfite (0.27 M, pH 7) on melting behavior of DNA, yeast RNA and their respective nucleosides was studied. It was found that bisulfite added not only to pyrimidine bases but also to purine bases of nucleic acids and of nucleosides. The addition products were stable at higher temperatures but reverted to parent compounds at room temperature. The only exception was the addition product of uridine which was stable at room temperature and could be isolated by paper chromatography in a 42-62% yield. Heating of DNA solutions in the presence of bisulfite to 95 degrees C caused a 90% loss of absorbance at 260 nm. On cooling, the absorbance was essentially recovered. When compared to the melting behavior of DNA in 0.27 M NaCl or 0.09 M Na2SO4 (same ionic strength), it was found that bisulfite destabilized double helical structure of DNA and that reversible addition of bisulfite did occur much below the melting temperature of DNA observed in the other two solvents.