(A) Formation of N3-methyladenine (3-mA) from the 24 h incubation of calf thymus DNA (100 μM nucleotide) with compounds 1–4, 7 and 8 at room temperature in 10 mM sodium cacodylate buffer (pH 7.0): 1 (■), 2 (●), 3 (▲), 4 (▼), 7 (◆), 8. (✖) Formation of 3-mA and N7-methylguanine (7-mG) from the incubation of 1 and 7 with calf thymus DNA in 10 mM cacodylate buffer (pH 7.0) at room temperature for 24 h.