With the spectacular advancement of NMR techniques and the flourishing of fluorine chemistry allowing the synthesis of various fluorinated molecules, (19)F NMR represents a compelling option for studying myriad biological events ranging from the structure and function of biomolecules, enzymatic mechanisms, and metabolic pathways, through to drug screening and discovery as well as medical imaging. In this tutorial review, we aim to provide readers with a brief overview of the recent applications of (19)F NMR in various areas relating to biological and biomedical research, together with a brief introduction of specific hardware improvements permitting the practical implementation of (19)F NMR.

In response to combined nitrogen starvation in the growth medium, the filamentous cyanobacterium Anabaena sp. PCC 7120 is able to develop a particular cell type, called a heterocyst, specialized in molecular nitrogen fixation. Heterocysts are regularly intercalated among vegetative cells and represent 5-10% of all cells along each filament. In unicellular cyanobacteria, the key Krebs cycle intermediate, 2-oxoglutarate (2-OG), has been suggested as a nitrogen status signal, but in vivo evidence is still lacking. In this study we show that nitrogen starvation causes 2-OG to accumulate transiently within cells of Anabaena PCC 7120, reaching a maximal intracellular concentration of Ϸ0.1 mM 1 h after combined nitrogen starvation. A nonmetabolizable fluorinated 2-OG derivative, 2,2-difluoropentanedioic acid (DFPA), was synthesized and used to demonstrate the signaling function of 2-OG in vivo. DFPA is shown to be a structural analogue of 2-OG and the process of its uptake and accumulation in vivo can be followed by 19 F magic angle spinning NMR because of the presence of the fluorine atom and its chemical stability. DFPA at a threshold concentration of 0.3 mM triggers heterocyst differentiation under repressing conditions. The multidisciplinary approaches using synthetic fluorinated analogues, magic angle spinning NMR for their analysis in vivo, and techniques of molecular biology provide a powerful means to identify the nature of the signals that remain unknown or poorly defined in many signaling pathways.cyanobacterium ͉ Krebs cycle ͉ nitrogen metabolism ͉ nutrient starvation ͉ signal transduction