Dynamics of a deuterated C-phycocyanin protein as studied by coherent inelastic neutron scattering

Quasi-elastic neutron scattering measurements of dry and 35% D2O hydrated amorphous protein powder of C-phycocyanin (0.175 g D2O/g protein) were made as a function of temperature ranging from 313 K down to 100 K. As the neutron scattering is dominated by coherent scattering, we are able to extract a coherent Debye-Waller factor. We observe a marked difference in the q-dependence of the Debye-Waller factor between the dry and hydrated proteins. Furthermore there is an interesting temperature dependence of the Debye-Waller factor which is quite different from that predicted for dense hard-sphere liquids.