Protein dynamics investigated by the neutron diffraction-hydrogen exchange technique.

A new approach, using neutron diffraction and the hydrogen exchange (H/D) technique, has been used to study the extent and nature of the inherent conformational fluctuations in the protein, trypsin. The observed pattern of exchange was used to investigate systematic relationships between exchangeable sites and structural and chemical properties of the molecule. Results of this analysis indicate that hydrogen-bonding structure is the dominant factor governing rates of exchange. The model of conformational mobility which best explains the experimental findings involves a localized disruption of the secondary structure within different regions of the protein molecule, each limited in extent to the breaking of a small number of hydrogen bonds.