2′-Deoxyribosylurea (urea) lesions form within DNA as a result of the cleavage of thymine from hydroxyl radicals resulting from ionizing radiation. In addition, urea lesions are able to form from 8-oxoguanine. Previous NMR studies of the urea lesion on the nucleoside level showed that the 2′-deoxyribose ring equilibrated between the alpha (α) and beta (β) configurations. In this study we examined the urea lesion in the single strand oligodeoxyribonucleotide 5′-(CTXA)-3′ (X=urea). Reverse phased HPLC revealed a ratio of 1:1 between two equilibrating species. In addition, trapping the different species in basic environment slowed the equilibration. NMR spectroscopy was used to definitely identify the two different species. NOESY and TOCSY spectra were used to assign the resonances of the different nucleotides. NOESY spectra revealed the identity of the two different species as α and β anomers of the urea lesion. TOCSY and one-dimensional NMR spectroscopy showed that the urea lesion was in the <i>anti</i> conformation regardless of the configuration the 2′-deoxyribose ring. The presence of the α anomer is a possible explanation as to why the lesion acts a strong block to replication.

Parsing the conformational and configurational equilibria of a 2′-deoxyribosylurea DNA adduct

252nd National Meeting (2016)

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