DYNAMICS OF HYDROGEN-ATOMS IN SUPEROXIDE-DISMUTASE BY QUASI-ELASTIC NEUTRON-SCATTERING

The low energy dynamics of the enzyme Cu,Zn superoxide dismutase have been investigated by means of quasielastic neutron scattering in the temperature range 4-320 K. Below 200 K the scattering is purely elastic, while above this temperature a pronounced decrease in the elastic intensity is observed, together with the onset of a small quasielastic component. This behavior is similar to that previously observed in other more flexible globular proteins, and can be attributed to transitions between slightly different conformational substates of the protein tertiary structure. The presence of only a small quasielastic component, whose intensity is less than or equal to 25% of the total spectrum, is related to the high structural rigidity of this protein.