TEMPERATURE-DEPENDENCE OF THE DYNAMICS OF SUPEROXIDE-DISMUTASE BY QUASI-ELASTIC NEUTRON-SCATTERING

The atomic dynamics of the enzyme Cu, Zn superoxide dismutase has been investigated by means of quasi-elastic neutron scattering in the temp erature range 4-320 K and in an extended momentum range up to 8.5 Angs trom(-1). Below 200 K the integrated elastic scattering intensity can be well described by a quasi-harmonic model, while above this temperat ure a pronounced decrease of the elastic intensity is observed, togeth er with the onset of a small quasi-elastic component. This behaviour, which is similar to that already observed in other globular proteins, can be attributed to the onset of torsional degrees of freedom which g ive rise to transitions between slightly different conformational subs tates of the protein tertiary structure.