Degradation of nucleic acids with ozone. V. Mechanism of action of ozone on deoxyribonucleoside 5'-monophosphates.

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Abstract
The degradation of dCMP [deoxy-CMP], dTMP, dAMP and dGMP with ozone [known to cause chromosome aberrations and mutational changes] in aqueous solution was investigated. The patterns of degradation were essentially the same as those of the corresponding ribonucleotides. The 2nd-order rate constants of the reactions as determined by stopped-flow spectrophotometry at pH 6.9 and 15.degree. C were 1.6 .times. 104/M per s and 1.4 .times. 103/M per s for dTMP and dCMP, respectively. The rate constants for dGMP and dAMP as estimated by a competitive technique under the same conditions were about 5 .times. 104/M per s and 2 .times. 102/M per s, respectively. The pH dependencies of the relative rate constants, krel, of nucleotide pairs as well as the effect of a radical scavenger on krel suggested that the predominant reaction pathway is the direct attack of ozone on the base moiety in the cases of dCMP, dTMP and dGMP. Radical reactions with the sugar moiety seemed to be predominant in the case of dAMP.