Figure 6.

Solvent-induced isotope shift observed for 5-fluoro cytidine modified oligonucleotides. (A) ¹⁹F NMR spectra of 5′-ACC^5FTTCCG recorded in varying mixtures of H₂O/D₂O. (B) Same for DNA hairpin S6b. Conditions: 0.3 mM oligonucleotide, 25 mM sodium arsenate buffer, pH 7.0, 300 K. (C) Deuterium exchange at the exocyclic amino group of 5-fluoro cytidine can result in four structures, causing individually shifted ¹⁹F resonance signals that are differently populated at different H₂O/D₂O ratios.