| Abstract
| - The base tautomerization processes of uracil/5-bromouracil were investigated in a microcosmic environmentwith both H2O and Na+ (W-M environment). It was found that uracil was more stable in the W-M environmentthan in the microcosmic environment with only water, which suggested that the metal ions and water workcooperated to maintain the classical nucleic acid bases. However, 5-bromouracil, a chemical mutagen, wasfound to be less stable than uracil in the W-M environment. Why the 5-bromouracil is easier to tautomerizeand therefore induce gene mutation was explained to some extent. Further research revealed that the watermolecule would assist the tautomerization in the W-M environment. However, the metal ions in differentregions play absolutely opposite roles: in one region, the metal ions can prevent the base from tautomerizing,whereas in another region, the metal ion can assist the tautomerization process. Furthermore, from the viewpointof ionization of the base, it seems BrU has a stronger tendency to lose the proton at N3, which is an intrinsicconsequence of the bromine atom and is not affected by the metal cation.
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