AbstractInteraction of a rigid fragment of B‐DNA (polyanionic as well as screened by Na+cations) with the flexible tripeptide Lys‐Ala‐Ala (in bothLandDconfigurations) were investigated with the aid of an empirical potential. The potential consists of intramolecular (MM2 potential) and intermolecular (pair potential described in reference 1) parts; hence total energy is formed by intra‐ and intermolecular components. The results demonstrate that intramolecular relaxation of the peptide results in a considerable decrease in total energy. While energies of DNA complexes with L‐Lys‐L‐Ala‐L‐Ala were comparable to those with D‐Lys‐D‐Ala‐D‐Ala the respective geometries exhib