ON THE PRESENCE OF ROTATIONAL EWALD ARTIFACTS IN THE EQUILIBRIUM AND DYNAMICAL PROPERTIES OF A ZWITTERIONIC TETRAPEPTIDE IN AQUEOUS-SOLUTION

The presence of Ewald artifacts in a molecular dynamics simulation of a zwitterionic tetrapeptide in aqueous solution has been investigated. Both equilibrium and dynamical aspects of the rotational behavior of the peptide were examined. The equilibrium distribution of rotational states obtained from a 10 ns simulation were consistent, within statis tical errors, with a random distribution free from Ewald artifacts. Th e rotational dynamics of the peptide was observed to obey simple Debye diffusion with a rotational diffusion rate in agreement with that pre dicted by a simple rotational diffusion model assuming no substantial long-lived water hydration shell. These results suggest that rotationa l Ewald artifacts will be negligible for small biomolecular simulation s in solvents with high relative permittivities. The data support the results obtained from a previous study of simpler model systems.