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In this paper,B3LYP and MP2 methods are used to investigate the binding energy of seventeen antiparallel and parallel β-sheet models. The results indicate that the binding energy obtained from B3LYP calculations is weaker than that obtained from MP2 calculations but the relative binding energy yielded by B3LYP is almost the same as that by MP2. For the antiparallel β-sheets in which two N―H···O═C hydrogen bonds can form either a large hydrogen-bonded ring or a small hydrogen-bonded ring,the binding energy increases obviously when one large ring unit is added,whereas it only changes slightly when one small ring unit is added because of the secondary electrostatic repulsive interaction existing in the small ring unit which is estimated to be about 20 kJ/mol. For the parallel β-sheet models,the binding energy increases almost exactly linearly with the increase of the chain length.
In this paper, B3LYP and MP2 methods are used to investigate the binding energy of seventeen antiparallel and parallel β-sheet models. The results that that binding energy obtained from B3LYP calculations is weaker than that obtained from MP2 calculations but the relative binding energy is by B3LYP is almost the same as that by MP2. For the antiparallel β-sheets in which two N-H ··· O═C hydrogen bonds can form either a large hydrogen-bonded ring or a small hydrogen-bonded ring, the binding energy increases obviously when one large ring unit is added, but it only changes slightly when one small ring unit is added because of the secondary electrostatic repulsive interaction existing in the small ring unit which is estimated to be about 20 kJ / mol. For the parallel β-sheet models, the binding energy increases almost exactly linearly with the increase of the chain length.