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.