Khaled M A, Sugano H, Urry D W
Biochim Biophys Acta. 1979 Apr 25;577(2):273-84. doi: 10.1016/0005-2795(79)90031-x.
The cyclododecapeptide, (Ala1-Pro2-Gly3-Val4-Gly5-Val6)2, was synthesized and its secondary structure was evaluated from extensive studies in dimethyl sulphoxide, trifluoroethanol and water using NMR methods. A selective decoupling technique in 13C-NMR has been utilized in order to assign the C=O carbon resonances. Temperature dependence of the peptide NH protons and the solvent perturbation of the peptide NH and C=O resonances show the occurrence in all solvents of a beta-turn (a 10-membered H-bond between the Val4 NH and Ala1 C=O) and a gamma-turn, an 11-membered H-bond between the Gly3 NH and the Gly5 C=O; and a possible 14-membered H-bond between the Ala1 NH and the Val4 C=O in dimethyl sulphoxide and trifluoroethanol. These secondary structural features are compared with the linear polyhexapeptide and found the the beta-turn and the gamma-turn are the common conformational features of these peptide systems.
合成了环十二肽(Ala1-Pro2-Gly3-Val4-Gly5-Val6)2，并通过在二甲亚砜、三氟乙醇和水中使用核磁共振方法进行广泛研究来评估其二级结构。利用13C-NMR中的选择性去耦技术来归属C=O碳共振峰。肽NH质子的温度依赖性以及肽NH和C=O共振峰的溶剂扰动表明，在所有溶剂中均存在β-转角（Val4 NH与Ala1 C=O之间形成10元氢键）和γ-转角（Gly3 NH与Gly5 C=O之间形成11元氢键）；在二甲亚砜和三氟乙醇中，Ala1 NH与Val4 C=O之间可能形成14元氢键。将这些二级结构特征与线性聚六肽进行比较，发现β-转角和γ-转角是这些肽体系共有的构象特征。
