Abstract: Radiation-induced damage of isolated glycyl–leucine (C₈H₁₆N₂O₃) molecules by the impact of He²⁺ ions has been studied. Relative cross sections of the main processes of charged state variation in collision parties and relative cross sections of fragmentation for singly and doubly charged molecular ions formed due to single collisions between glycyl–leucine molecules and He²⁺ ions have been determined for the first time. Optimized geometry of the molecule and singly charged molecular ion of glycyl–leucine has been calculated by method of density functional theory.