19F NMR of pentafluorophenylalanine in proteins: slow ring flips and allosteric effects

Gottfried Otting (Australian National University, Australia)

Abstract: Using genetic encoding, single phenylalanine residues were replaced by pentafluorophenylalanine. The 19F-NMR spectrum shows that the C6F5 group rotates much more slowly than the phenyl rings of canonical phenylalanine residues. Crystal structures show minimal structural perturbation. Two applications stand out: (a) The five 19F-NMR resonances of a slowly rotating C6F5 group enable simple measurements of the aromatic ring flips even in big proteins (> 40 kDa) without isotope labelling. The ring flip rates are a measure of local protein malleability and change in response to ligand binding. (b) The 19F chemical shifts are very sensitive reporters of allosteric effects.