Chauhan V S, Uma K, Kaur P, Balaram P
Biopolymers. 1989 Mar;28(3):763-71. doi: 10.1002/bip.360280306.
The conformation of an acyclic dehydrophenylalanine (delta Z-Phe) containing hexapeptide, Boc-Phe-delta Z-Phe-Val-Phe-delta Z-Phe-Val-OMe, has been investigated in CDCl3 and (CD3)2SO by 270-MHz 1H-nmr. Studies of NH group solvent accessibility and observation of interresidue nuclear Overhauser effects (NOEs) suggest a significant solvent-dependent conformational variability. In CDCl3, a population of folded helical conformations is supported by the inaccessibility to solvent of the NH groups of residues 3-6 and the detection of several NiH----Ni + 1H NOEs. Evidence is also obtained for conformational heterogeneity from the detection of some Ci alpha H----Ni + 1H NOEs characteristic of extended strands. In (CD3)2SO, the peptide largely favors an extended conformation, characterized by five solvent-exposed NH groups and successive Ci alpha H----Ni + 1H NOEs for the L-residues and Ci beta H----Ni + 1H NOEs for the delta Z-Phe residues. The results suggest that delta Z-Phe residues do not provide compelling conformational constraints.
已通过270兆赫兹的¹H-核磁共振在CDCl₃和(CD₃)₂SO中研究了含无环脱氢苯丙氨酸（δZ-Phe）的六肽Boc-Phe-δZ-Phe-Val-Phe-δZ-Phe-Val-OMe的构象。对NH基团溶剂可及性的研究以及对残基间核Overhauser效应（NOEs）的观察表明存在显著的溶剂依赖性构象变异性。在CDCl₃中，残基3-6的NH基团对溶剂不可及以及检测到几个NiH----Ni + 1H NOEs，支持了折叠螺旋构象的存在。从检测到一些伸展链特有的CiαH----Ni + 1H NOEs也获得了构象异质性的证据。在(CD₃)₂SO中，该肽主要倾向于伸展构象，其特征为五个溶剂暴露的NH基团，L-残基有连续的CiαH----Ni + 1H NOEs，而δZ-Phe残基有CiβH----Ni + 1H NOEs。结果表明，δZ-Phe残基并未提供令人信服的构象限制。
