NMR-STUDIES OF ORTHO AND META-FLUOROCINNAMATE-ALPHA-CHYMOTRYPSIN COMPLEXES

Fluorine magnetic resonance spectroscopy has been used to examine the complexes formed between o‐ and m‐fluorocinnamate ions and the enzyme α‐chymotrypsin. Study of the frequency dependence of fluorine spin‐lattice and spin‐spin relaxation rates suggests that, like the p‐isomer, both the o‐ and m‐fluorocinnamates bind equally well to monomeric, dimeric and trimeric forms of the protein. Dipole‐dipole interactions with protons of the enzyme play an important role in relaxing the protein‐bound fluorine nucleus. Various deuterated forms of the ortho isomer were used to obtain evidence suggesting that the conformation of this molecule bound to the enzyme is similar if not identical to the conformation found in free solution. NMR methods were used to estimate the rates of dissociation of the complexes and the chemical shifts of the bound fluorine atoms were determined to be substantially downfield of their positions in the absence of enzyme. Copyright © 1979 Heyden & Son Ltd.