the ph-dependence of the 3h to 1h exchange between water and c ( 8 ) h groups of purine , adenine , 9-methyladenine , 7-methyladenine , hypoxanthine , guanine , xanthine as well as c ( 2 ) h groups of imidazole and benzimidazole was studied .
C0034140
purine
C0001407
adenine