2.1 Preparation of AFB1-FapyGua-containing oligodeoxynucleotides
The 11-mer oligodeoxynucleotides site-specifically modified with AFB1-FapyGua were prepared from unmodified oligodeoxynucleotides containing the unique N7-guanine alkylation site (5′-CCATAGC TACC-3′, 5′-CCATCGC TACC-3′, 5′-CCATTGC TACC-3′, or 5′-CCATCGA TACC-3′, where the target and neighboring sites are underlined). These were annealed with the corresponding 6-mer oligodeoxynucleotides (5’-TAGCTA-3’, 5’-TAGCGA-3’, 5’-TAGCAA-3’, and 5’-TATCGA-3’) to form partially double-stranded DNA structures and reacted with AFB1 exo -8,9-epoxide. The conditions for chemical modifications, purification by reverse-phase HPLC, and characterization by mass spectrometry were previously described (Li et al. 2015; Tomar et al. 2021).