Rabbits ingesting 4-fluorophenylalanine are known to incorporate small amounts of this fluorinated amino acid into their proteins. Carbonic anhydrase I isolated from the erythrocytes of animals so maintained exhibits a well-resolved fluorine NMR signal for each phenylalanine in the sequence. The chemical shifts of most of these signals respond to the binding of inhibitors, suggesting that most if not all of the tertiary structure of the enzyme adjusts to the presence of inhibitors at the active site.
