HAIRPIN-FORMING PEPTIDE NUCLEIC-ACID OLIGOMERS

A series of partially self-complementary peptide nucleic acid (PNA) ol igomers was prepared. Examination of their melting behavior, circular dichroism spectra, and fluorescence properties reveals that these PNA oligomers exist as stem-loop (''hairpin'') structures. Fluorescence is readily observed in hairpins containing a covalently linked, emissive acridine derivative which is, at least partially, intercalated in the duplex region of the PNA hairpin. The acridine fluorescence is quench ed when an anthraquinone derivative is covalently attached to the PNA so that it is bound near the acridine in the hairpin structure. Acridi ne fluorescence is restored in hairpins containing both the anthraquin one and the acridine by increasing the temperature and melting the str ucture to its linear form or by opening the hairpin through formation of a hybrid duplex with complementary DNA. The latter process may form the basis for development of selective and sensitive DNA assays.