5-(Pyren-1-yl)uracil as a base-discriminating fluorescent nucleobase in pyrrolidinyl peptide nucleic acids.

A pyrene-labeled uridine (U(Py)) monomer for a pyrrolidinyl peptide nucleic acid with an alternating proline/2-aminocyclopentanecarboxylic acid backbone (acpcPNA) was synthesized and incorporated into the PNA. The U(Py) base in acpcPNA could specifically recognize the base A in its complementary DNA strand as determined by thermal denaturation (T(m)) experiments. The fluorescence of the U(Py)-containing single-stranded acpcPNA was very weak in aqueous buffer. In the presence of a complementary DNA target, the fluorescence was enhanced significantly (2.7-41.9 folds, depending on sequences). The fluorescence enhancement was specific to the pairing between U(Py) and dA, making the U(Py)-modified acpcPNA useful as a hybridization-responsive fluorescence probe for DNA-sequence determination.