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The first non‐helical Aib‐containing hexapeptide: The crystal structure of Z‐Gly‐Aib‐Gly‐Aib‐Gly‐Aib‐OtBu
Journal of Peptide Science ( IF 1.8 ) Pub Date : 2021-02-17 , DOI: 10.1002/psc.3307
Renate Gessmann 1 , Hans Brückner 2 , Kyriacos Petratos 1
Affiliation  

The synthetic peptide Z‐Gly‐Aib‐Gly‐Aib‐Gly‐Aib‐OtBu was crystallized from a mixture of ethyl acetate and n‐hexane. The crystals belong to the centrosymmetric space group Pbca. There are three molecules in the asymmetric unit. The three molecules differ mainly in the Z‐group conformation. The first Gly residue adopts a fully extended conformation, residues 2 and 3 lie in the left‐handed helical region, residues 4 and 5 in the right‐handed helical region, and residue 6 again in the left‐handed helical region of the Ramachandran plot. There are only two of four possible intramolecular hydrogen bonds formed, namely, between Aib4 and Gly1 forming a β‐turn of type III′ and between Aib6 and Gly3 forming a β‐turn of type I. The inverted molecules (by space group symmetry) lie in the regions with opposite handedness and form β‐turns of type III and I′. In contrast to all known long synthetic and naturally occurring Aib‐containing peptides that fold as 310‐ or α‐helix, Z‐(Gly‐Aib)3‐OtBu folds in a quite flat structure from which only the protecting groups bulge out.

中文翻译:

第一个非螺旋型 Aib 六肽:Z-Gly-Aib-Gly-Aib-Gly-Aib-OtBu 的晶体结构

合成肽Z-甘氨酸-AIB酰-Gly-AIB-甘氨酸-AIB-O卜从乙酸乙酯和的混合物中结晶Ñ正己烷。晶体属于中心对称空间群Pbca. 不对称单元中有三个分子。这三个分子的主要区别在于 Z 基团构象。第一个 Gly 残基采用完全延伸的构象,残基 2 和 3 位于左旋螺旋区域,残基 4 和 5 位于右旋螺旋区域,残基 6 再次位于拉马钱德兰图的左旋螺旋区域. 四个可能的分子内氢键中只有两个形成,即 Aib4 和 Gly1 之间形成 III' 型 β-转角,Aib6 和 Gly3 之间形成 I 型 β-转角。 反转分子(通过空间群对称性)位于具有相反旋向性的区域并形成 III 型和 I' 型的 β 转角。与折叠为 3 10螺旋或 α 螺旋的所有已知长合成和天然含有 Aib 的肽相比,Z-(Gly-Aib)3 -O t Bu 折叠成一个非常平坦的结构,只有保护基团从中凸出。
更新日期:2021-04-05
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