Calculation Of The Oligopeptide Molecular Energies In Terms Of ABEEMσπ/MM Method

The peptide of the organism haves important biologic functions, it exerts biologic active action in cells at a certain extant. So sdudying on it is considerably significant. The molecular energies of the oligopeptides and the different conformations of dipeptides are researched in this paper.Atom-bond electronegalitivity equalization method(ABEEMaσπ) and molecular mechanics(MM) inosculates together, namely ABEEMσπ/MM. The molecular energies of the oligopeptides and the different conformations of dipeptides are calculated by ABEEMσπ/MM method. Firstly, the valence-state energy parameters of the different types of atoms of the model molecules have been calibrated to fit the molecular energies of the ab initio (MP2/6-311++G(d,p)) method. The molecular energies of the oligopeptides are obtained using these valence-state energy parameters by ABEEMσπ/MM. Compared with the molecular energies calculated by MP2/6-311+G(d,p) method, the absolute derivation is less than 9.0000 kcal/mol and the relative deviation is less than 19.0000×10-6, the RMSD is 3.4500 kcal/mol and the relative RMSD is 6.9190×10-6. Besides, the molecular energies of the different conformations of dipeptides are calculated by ABEEMσπ/MM. Compared with the molecular energies calculated by MP2/6-311+G(d,p) method, the absolute derivation is less than 2.0000 kcal/mol and the relative deviation is less than 4.0000×10-6, the RMSD is 1.0647 kcal/mol and the relative RMSD is 2.7016×10-6. Their energy results are in accordance with the molecular energies of the ab initio (MP2/6-311++G(d,p)) method. At the same time, the valence-state energy parameters are commendably transferable. Furthermore, consuming time on computing molecular energy by the ABEEMσπ/MM is quite less than the ab initio(MP2/6-311++G(d,p)) method. This work will establish a good foundation for other larger biologic molecular energies and the correlative properties,et al.