查看文章

Peptide nucleic acid (PNA) is a DNA analogue in which the negatively charged sugar phosphate backbone has been substituted by uncharged N-(2-aminoethyl)glycine units. The study of a PNA−DNA duplex and the corresponding DNA−DNA duplex gives a unique opportunity to compare two polyelectrolytes with virtually identical geometry but greatly different linear charge density. The results provide a basis for a study of the applicability of the Poisson−Boltzmann (PB) and counterion condensation (CC) theories. UV and circular dichroism spectroscopy as well as isothermal titration calorimetry (ITC) have been used to study the effect of different ions on the stability and conformation of PNA−DNA, PNA−PNA, and DNA−DNA duplexes having the same base sequences. Cations in general destabilize both antiparallel (N/3‘) and parallel (N/5‘) PNA−DNA duplexes whereas they stabilize the DNA−DNA duplex. Studies …