1,8-Naphthyridin-2,7-(1,8H)-dione is an effective mimic of protonated cytosine in peptide nucleic acid triplex recognition systems

A novel bicyclic mimic of protonated cytosine [1,8-naphthyridin-2,7-(1,8H)-dione, (K)] for Hoogsteen type triplex recognition of guanine has been designed for incorporation into peptide nucleic acids. Bis-PNA clamps with the K base incorporated in the Hoogsteen strand showed a significant stabilization of the triplexes at pH 7 as compared to similar triplexes with PNA oligomers containing either cytosine (6.7degreesC per unit) or pseudoisocytosine (1.5degreesC per unit). Cooperative stabilization was observed when the K units were placed in adjacent positions (similar to3degreesC per unit). (C) 2002 Elsevier Science Ltd. All rights reserved.