Strand invasion of extended, mixed-sequence B-DNA by gammaPNAs.

In this communication, we show that peptide nucleic acids (PNAs) with lengths of 15-20 nucleotides, when preorganized into a right-handed helix, can invade mixed-sequence double-helical B-form DNA (B-DNA). Strand invasion occurs in a highly sequence-specific manner through direct Watson-Crick base pairing. Unlike the previously developed double-duplex invasion strategy, which requires simultaneous binding of two strands of pseudocomplementary PNAs to DNA, only a single strand of gammaPNA is required for invasion in this case, and no nucleobase substitution is needed.