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Wednesday, February 3, 2021

Electrostatics Favor PNA : DNA Stability over Stereochemistry in Pyrrolidine‐Based Cationic Dual‐Backbone PNA Analogues

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Electrostatics Favor PNA : DNA Stability over Stereochemistry in Pyrrolidine‐Based Cationic Dual‐Backbone PNA Analogues

A dual diaminopyrrolidine based peptide nucleic acid (dapPNA) monomer that give rise to two different PNA backbones (shown in blue & red) was synthesized using orthogonal solid phase chemistry. Presence of free amino group makes PNA cationic and thus not only show high thermal stability in complexation with DNA but also overcomes the unfavorable stereochemical effects.


Abstract

Modifications to the peptide nucleic acid (PNA) backbone has been well known to alter the thermodynamical parameters of PNA : DNA complexes to broaden their utility for different applications. Electrostatic interactions between a modified PNA having a positively charged backbone and the negatively charged DNA has been shown to enhance thermal stabilities of PNA : DNA complexes at various instances. On the other hand, chiral introduction in PNA backbone leads to stereochemical preference that affects binding properties. However, the interplay between electrostatics and stereochemistry has not been systematically studied so far. Herein, we report the synthesis and biophysical characterization of cationic PNA named dapPNA, first of its kind, having a dual PNA backbone constituting of a pyrrolidine ring having a β‐substitution. One of the aims of this study was to investigate the role of electrostatics over stereochemical preferences. The results show that electrosta tic attraction between cationic dapPNA and negatively charged DNA overcomes the unfavorable stereochemical effects and enhances stability of PNA : DNA complexes. Moreover, two different PNA backbones derived from a single PNA monomer expands the repertoire of pyrrolidine based PNA analogues.

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