U. Hansler et Se. Rokita, ELECTROSTATICS RATHER THAN CONFORMATION CONTROL THE OXIDATION OF DNA BY THE ANIONIC REAGENT PERMANGANATE, Journal of the American Chemical Society, 115(19), 1993, pp. 8554-8557
Kinetic study was used to compare permanganate oxidation of oligonucle
otides and evaluate the structural basis for its specificity of reacti
on. The rate of oligonucleotide consumption was consistently dominated
by reaction of unpaired and solvent accessible thymine residues, the
primary targets of modification. Formation of fully complementary dupl
ex structures suppressed reaction of the single-stranded oligonucleoti
des by as much as 20-fold and revealed a basal rate of modification th
at no longer correlated to the presence of thymine. Insertion of a mis
paired or unpaired thymine into a duplex structure modestly enhanced t
he overall degradation rate of DNA. While steric effects should not be
discounted, electrostatic effects appeared to be the major determinan
t in permanganate selectivity. The oxidation rate of thymidine 5'-mono
phosphate and thymine residues in a single-stranded oligonucleotide ap
proached the rate of thymidine only when high salt concentration was p
resent to shield the repulsion of the anionic reactants. Oxidation of
duplex structures was also activated by 10- to 25-fold when the sodium
chloride concentration was increased from 0.1 to 4.0 M.