In the present article, we address the question that how important role do the Quantum Mechanic (QM) and Molecular Mechanics (MM) forces play in ligand docking on protein, via the use semi-quantum relaxation approach (SQRA) using different forces, . quantum, Van der Waals and Coulomb ones, in the process of ligand - protein docking. The QM approximation is applied to calculate the QM forces of neighbor protein-atoms acting on ligands. The L-J 6-12 empirical potential model and Coulomb rule are applied to calculate the forces from the rest protein-atoms on each ligand - atom. This work intent to investigate the intrinsic role of QM forces in the ligand-protein docking calculation then interprets the interaction between ligands and protein. The calculation results shown that, the ligand-protein complex is kept in by stable state not by covalent bonding but darling interaction which could be calculated by QM appoximation.
