Vibrational excitations of proteins and their hydration water in the far-infrared range

Incoherent neutron scattering has been used to single out the vibrational contribution from maltose binding protein (MBP) and its hydration water in the energy range 1 meV-80 meV. The vibrational density of states from both protein and hydration water have been investigated by measuring respectively dry and D2O-hydrated isotopically natural MBP and dry and H2O-hydrated perdeuterated MBP. Molecular dynamics simulations done on the same system allow us to attribute the protein inelastic features. The inelastic behavior of the biomolecule seems to be largely independent on the presence of solvent. Conversely, protein hydration water exhibits remarkable differences with respect to hexagonal ice in the whole spectral range, with clear similarities to amorphous phases of ice. (C) 2013 Elsevier B. V. All rights reserved.