A simplified force field for describing vibrational protein dynamics over the whole frequency range

The empirical force fields used for protein simulations contain short-range d terms (chemical bond structure, steric effects, van der Waals interaction s) and long-ranged electrostatic contributions. It is well known that both components are important for determining the structure of a protein. We sho w that the dynamics around a stable equilibrium state can be described by a much simpler midrange force field made up of the chemical bond structure t erms plus unspecific harmonic terms with a distance-dependent force constan t. A normal mode analysis of such a model can reproduce the experimental de nsity of states as well as a conventional molecular dynamics simulation usi ng a standard force field with long-range electrostatic terms. This finding is consistent with a recent observation that effective Coulomb interaction s are short ranged for systems with a sufficiently homogeneous charge distr ibution. (C) 1999 American Institute of Physics. [S0021-9606(99)52348-9].