Site-specific labeling of DNA sequences containing phosphorothioate diesters

A phosphorothioate diester can be incorporated site-specifically into DNA sequences to provide a nucleophilic site that is amenable to alkylation by labels containing haloacetamide, aziridine sulfonamide, or γ-bromo-α,β-unsaturated carbonyl functionalities. Labeling reactions proceed most efficiently at 50 o C in the pH range 5.0-8.0 and require a number of hours for completion. HPLC techniques employing reversed-phase columns can be used to rapidly purify the labeled materials, and a variety of examples are shown including the purification of a site-specifically labeled 30-mer