Peptide nucleic acids (PNA) incorporating nucleic acid bases into an achiral
polyamide backbone bind to DNA in a sequence-dependent manner. The structure of
a PNA-ribonucleic acid (RNA) complex was determined with nuclear magnetic
resonance methods. A hexameric PNA formed a 1:1 complex with a complementary RNA
that is an antiparallel, right-handed double helix with Watson-Crick base
pairing similar to the "A" form structure of RNA duplexes. The achiral
PNA backbone assumed a distinct conformation upon binding that differed from
previously proposed models and provides a basis for further structure-based
design of antisense agents.
