- 作者: Yun-Dong Wu and De-Ping Wang
- 中文摘要: Conformational features of a,b-disubstituted β2,3-dipeptide models have been studied with quantum mechanics method. Geometries were optimized with the HF/6-31G** method, and energies were evaluated with the B3LYP/6-31G** method. Solvent effect was evaluated with the SCIPCM method. For (2S,3S)- β2,3-dipeptide model 1, a six-membered-ring hydrogen bonded structure is most stable. However, the conformation corresponding to the formation of the 14-helix is only about 1.7 kcal/mol less stable in methanol solution, indicating that the 14-helix is favored if a (2S,3S)- β2,3-polypeptide contains more than 5 residues. On the other hand, the conformation corresponding to the formation of b-sheet is most stable for (2R,3S)- β2,3-dipeptide model 2, suggesting that this type ofβ-peptides is intrinsically favored for the formation of b-sheet secondary structure.
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