(a) HPLC chromatogram of a mixture from reaction between a 12-mer sequence and N-trifuloroacetyl-N-acetoxy-2-aminofluorene. The mono- (G3, G1, G2) and di- (G1G3, G2, G3, G1G2) AF adducts eluted in the 30–40 and 50–60 min ranges, respectively. (b) On-line UV spectra of the control (unmodified dodecamer), mono- and di-AF adducts. (c) Purity check of all the fractions.