Structure and dynamics of alpha-chymotrypsin-N-trifluoroacetyl-4-fluorophenylalanine complexes.

Fluorine NMR lineshape, relaxation and Overhauser effect data collected at 282 and 470 MHz have been used to obtain information about the nature of complexes formed between N-trifluoroacetyl-4-fluorophenylalanine and the enzyme chymotrypsin. Systems involving both enantiomers have been examined as well as derivatives of these in which the aromatic ring hydrogens have been replaced by deuterium. The enzyme-induced fluorine chemical shift effects and the dynamics of molecular motions of the fluorophenyl ring at the respective binding sites appear to be similar in both complexes and, where comparable, the results are in agreement with data obtained at lower frequencies that have been reported by other workers. The dynamics of the fluoroaromatic ring in these complexes are significantly different from those observed in a closely related acylated enzyme.