pounds 2 and 3 also exhibited identical cleavage profiles (Fig. 3, lanes 7 and 9), but different from that of 1 (Fig. 3, lane 1). The susceptibility of conjugated sulfones to nucleophilic attack is also in line with the proposed mechanism. ['3] The selectivity of compounds 1-3 in recognizing DNA regions may reflect not only their reactivity towards individual bases, but also local DNA shapes. This selectivity may be amplified synergistically by attaching these new DNA-cleaving moieties onto sequence-specific delivery systems.