Ribose 2‘-F Labeling:  A Simple Tool for the Characterization of RNA Secondary Structure Equilibria by 19F NMR Spectroscopy

We present a facile 19F NMR spectroscopic approach for the characterization of bistable RNA. The concept is based on the site-specific labeling of RNA with single 2‘-deoxy-2‘-fluoro (2‘-F) nucleosides. Depending on the position of the 2‘-F label (either within a double helix or a single-stranded region), significantly different 19F chemical shifts were observed and assigned to the particular alternative folds. This has been exemplified for a series of bistable RNAs. The approach is promising for the detailed investigation of complex RNA folding pathways.