Comparative study of spontaneous deamination of adenine and cytosine in unbuffered aqueous solution at room temperature

Highlights: • The rate of hydrolytic deamination of adenine is greatly affected by the absence of buffers. • Adenine deaminates significantly faster than cytosine in unbuffered nanopure water. • The deamination rate depends on the interaction sites between water and DNA base molecules. Adenine in unbuffered nanopure water at a concentration of 2 mM is completely deaminated (>99%) to hypoxanthine at room temperature in ca. 10 weeks, with an estimated half-life (t_1/2) less than 10 days, about six orders of magnitude faster than previously reported. Cytosine is not deaminated under the same condition, even after 3 years. This is in contrast to previous observations that cytosine deaminates 20–40 times faster than adenine free base, in nucleoside, in nucleotide and in single-stranded DNA in buffered neutral aqueous solutions.