Reactivity of nucleotides and polynucleotides toward hydroxyl radical in aqueous solution.

Rate constants for the reactions of hydroxyl radicals with nucleotides, polynucleotides, and related compounds were determined with a competition method using p-nitrosodimethylaniline. Reactivity of mononucleotides toward hydroxyl radicals decreases with increasing number of phosphate group. For polynucleotides, the reactivity per nucleotide unit was found to be much less than the corresponding mononucleotide and to depend on their conformation. The more rigid the conformation, the smaller the rate constant. The reactivity of polynucleotides was enhanced after heat-treatment at 80°C. The results are discussed in terms of steric hindrance and of reaction of a macromolecule with a small molecule in aqueous solution.