Transalkylation of phosphotriesters using cob(I)alamin: Toward specific determination of DNA-phosphate adducts

The supernucleophilic cobalt compound, cob(I)alamin, has been kinetically c haracterized with respect to its ability to bring about transalkylation of adducts to DNA phosphates (phosphotriesters). The reactivity of cob(I)alami n toward different phosphotriesters (model compounds and methylated DNA), a s well as its specificity toward DNA-phosphate adducts, has been investigat ed. Through nucleophilic displacement on the alkyl by cob(I)alamin, the alk yl groups (methyl and ethyl) were transferred from phosphotriesters within minutes at room temperature. In contrast, methylated nucleosides (base addu cts) were stable in the presence of cob(I)alamin.