Microcalorimetry and fluorescence show stable peptide nucleic acid (PNA) duplexes in high organic content solvent mixtures

The selectivity of nucleic acid hybridisation can be exploited to template chemical reactions, enabling materials discovery by chemical evolution. However, to date the range of reactions that can be used has been limited to those that are compatible with aqueous media, since the addition of organic co-solvents can have a large impact on the stability of nucleic acid duplexes. Peptide nucleic acids (PNAs) are promising in this regard because previous studies have suggested they may be stable as duplexes in high organic content solvent mixtures. Here, we use micro-differential scanning calorimetry (micro-DSC) to confirm for the first time that double-stranded PNA (dsPNA) is stable in N,N-dimethylformamide (DMF)/water mixtures up to 95 vol% DMF. Using fluorescence, we corroborate these results and show that the isothermal annealing of PNA in high DMF content solution is also rapid. These findings suggest that PNA could enable the use of a range of water-sensitive chemistries in nucleic acid templating applications.