Dynamical interaction between protein molecules and their hydration shell

The hydration shell of a protein molecule influences its functional important dynamics while the protein molecule influences the hydration shell. Neutron scattering experiments have been used to separate both effects. Neutron crystallography is used to determine the positions and the mean square displacements, (x²), of the protons in met-myoglobin. Mean square displacements obtained by incoherent neutron scattering stem from motions occurring on a time scale faster than 100 ps. The combination of the two experimental results allows to separate three types of protein protons. The (x²)-values of lysine protons stem from motions faster than 100 ps. Half of the (x²)-values of methyl protons is caused by motions faster than 100 ps, the other halve comes from slower motions. The backbone protons move slower than 100 ps. Incoherent neutron scattering on a perdeuterated myoglobin with a ¹H₂O hydration shell allowed the study of the diffusion in this shell.