Mixed pyrimidine-purine peptide nucleic acids (PNAs) composed of thymines and guanines are shown to form a PNA(2)-DNA triplex with Watson-Crick complementary adenine-cytosine oligonucleotides and to bind complementary adenine-cytosine targets in double stranded DNA by helix invasion. These results for the first time demonstrate binding of an unmodified PNA oligomer to a mixed pyrimidine-purine target in double stranded DNA and illustrate a novel binding mode of PNA.
Center for Biomolecular Recognition, Department for Biochemistry and Genetics, Biochemistry Laboratory B, The Panum Institute, Blegdamsvej 3c, DK-2200N Copenhagen, Denmark. pen@imbg.ku.dk
