Figure 2.

Schematic drawing of PNA binging modes, targeting to dsDNA. DNA is drawn as a ladder and PNA molecules are in thick structures. Triplex complex is formed by cytosine rich PNA targeting to homopurine target. Triplex invasion structure leads to the formation of a loop. In this structure, one strand of PNA binds based on Watson-Crick rule, and another strand binds through Hoogsteen bond. Duplex invasion has no sequence constraints. Double duplex invasion is formed by PNAs containing modified bases.³