Molecular dynamics simulations of the zinc finger domain of protein Zif268, in a complex with a high affinity DNA sequence, yields a globally stable system with small yet significant readjustments with persistence time of the order of 1.1ns. The results confirm the quality of the standard GROMOS87 force field with a corrected solvent-to-solute interaction that does not affect the water-water SPC interactions nor the intra-molecular cohesive forces. Specificity determinants are discussed. The simulations of DNA alone, with the same force field, showed the important role played by the solvent and the symmetry of the counterion distribution. (Tapia & Velázquez, J. Am. Chem. Soc., 119, 5934, 1997) In the present work, this feature was retained when appropriate. The results for root mean square deviations and temperature B-factors illustrate the reliability of this approach. The structure of DNA is held by its interactions with the zinc finger protein. This behavior is not much affected by the slow whithering away of finger-1 from DNA. The factors contributing to the molecular stability found in GROMOS' potential energy function appear to be sufficient to yield stable fluctuation patterns when surrounding medium effects are properly included.