Enlarging the scenario of site directed ¹⁹F labeling for NMR spectroscopy of biomolecules

The possibility of using selectively incorporated F-19 nuclei for NMR spectroscopic studies has retrieved increasing interest in recent years. The high gyromagnetic ratio of F-19 and its absence in native biomolecular systems make this nucleus an interesting alternative to standard H-1 NMR spectroscopy. Here we show how we can attach a label, carrying a F-19 atom, to protein tyrosines, through the use of a specific three component Mannich-type reaction. To validate the efficacy and the specificity of the approach, we tested it on two selected systems with the aid of ESI MS measurements.