A biomimetic four-helix bundle with a binuclear active site (DF1), bearing Zn, Mn or Fe as transition metals, has been synthesized and characterized. The carboxylate bridged binuclear motif of DF1 resembles the active site of numerous binuclear enzymes, such as Manganese Catalase, Methane Monoxygenase (MMO), etc. Due to the crucial chem. and biol. relevance of binuclear enzymes in hydrolytic as well as redox active processes, we have performed a systematic study of the structural properties of the dizinc analog of DF1 through ab initio and hybrid QM/MM Car-Parrinello mol. dynamics simulations. Different quantum mech. models of the active site have been chosen in order to gain a qual. view of how the first and second shell ligands can tune structural and dynamical properties of the active site. In addn., the geometrical restraints and the electrostatic stabilization provided by the whole structure have been explicitly considered, performing QM/MM mol. dynamics simulations. [on SciFinder (R)]