We have performed Monte Carlo replica-exchange method calculations on the gas phase tryptophan-glycine dipeptide in a static electric field. At low electric field, the average dipole of the molecule follows the Langevin-Debye equation. At high electric field, a deviation from this law is observed and the analysis of the results shows that the external field modifies the conformation of the molecules. This opens the way to a possible control of the conformation of gas phase biomolecules with static electric fields. (C) 2004 Elsevier B.V. All rights reserved.