Andreetto Erika, Peggion Cristina, Crisma Marco, Toniolo Claudio
Institute of Biomolecular Chemistry, CNR, Department of Chemistry, University of Padua, 35131 Padua, Italy.
Biopolymers. 2006;84(5):490-501. doi: 10.1002/bip.20534.
A set of four hexapeptide sequences, each characterized by four strongly helicogenic Aib residues and all combinations of two isomeric Ile/aIle residues at positions 2 and 5, was synthesized by solution methods and fully characterized. A detailed solution (by FT-IR absorption, NMR, and CD techniques) and solid/crystalline state (by X-ray diffraction) conformational investigation allowed us to validate our assumption that all four peptides are folded in well-developed 3(10)-helical structures. However, the most relevant conformational conclusion extracted from the present 3D-analysis is that the handedness of the 3(10)-helical structures formed does not seem to be sensitive to the configurational change at the beta-carbon atom of the constituent Ile versus the diastereomeric aIle residues (in other words, the dominant control on this important structural parameter appears to be exerted by the chirality of the amino acid alpha-carbon atom). These results complement published findings on the diverging relative stabilities of the intermolecularly H-bonded beta-sheet structures generated by Ile versus aIle homo-oligopeptides.
通过溶液法合成了一组四个六肽序列，每个序列的特征是含有四个具有强螺旋形成能力的Aib残基，以及在第2和第5位的两种异构Ile/aIle残基的所有组合，并对其进行了全面表征。通过详细的溶液（通过傅里叶变换红外吸收、核磁共振和圆二色技术）和固态/晶体状态（通过X射线衍射）构象研究，我们得以验证我们的假设，即所有四个肽都折叠成发育良好的3(10)-螺旋结构。然而，从目前的三维分析中得出的最相关的构象结论是，所形成的3(10)-螺旋结构的手性似乎对组成Ile与非对映异构aIle残基的β-碳原子上的构型变化不敏感（换句话说，对这一重要结构参数的主要控制似乎是由氨基酸α-碳原子的手性施加的）。这些结果补充了已发表的关于由Ile与aIle同聚肽产生的分子间氢键β-片层结构不同相对稳定性的研究结果。
