Analysis of low-frequency motions in proteins by computer simulation and neutron scattering

The combination of molecular simulations and thermal neutron scattering is a powerful tool to analyze the dynamics of macromolecular systems on pico- to nanosecond time scales. The main goal is the assignment of parts of the neutron spectrum to specific molecular motions or to a certain type of motion. We show recent examples where Molecular Dynamics simulations and normal mode analysis are used to analyze quasielastic and inelastic neutron scattering spectra of myoglobin. Our analysis allows to obtain a general view of protein dynamics on the time scale of inelastic neutron scattering and extends earlier work on quasielastic scattering. We show also that normal mode analysis with much simplified force fields yields the vibrational density of states with about the same accuracy as full Molecular Dynamics simulations. This allows to obtain estimates of inelastic neutron spectra from simulation with low computational effort.