Figure 17.
(A) Structure of peptide nucleic acid (PNA) next to natural DNA (left) and (B) illustration of the binding of duplex DNA by two PNA strands at low ionic strength, forming a “D-looped” structure. One strand (at a homopurine site) is bound in a triplex with two identical PNA strands, and the unbound strand is displaced from the double helix.29,64