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首页> 外文期刊>Chemistry: A European journal >Engineering a b-Helical d,l-Peptide for Folding in Polar Media
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Engineering a b-Helical d,l-Peptide for Folding in Polar Media

机译：工程化b螺旋d，l肽以在Polar Media中折叠

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摘要

b Helices—helices formed by alternating d,l-peptides and stabilized by b-sheet hydrogen bonding—are found naturally in only a handful of highly hydrophobic peptides. This paper explores the scope of b-helical structure by presenting the first design and biophysical characterization of a hydrophilic d,l-peptide, 1, that forms a b helix in methanol. The design of 1 is based on the b-hairpin/b helix—a new supersecondary that had been characterized previously only for hydrophobic peptides in nonpolar solvents. Incorporating polar residues in 1 provided solubility in methanol, in which the peptide adopts the expected b-hairpin/bhelical structure, as evidenced by CDanalytical ultracentrifugation (AUC), NMR spectroscopy, and NMR-based structure calculations. Upon titration with water (at constant peptide oncentration), the structure in methanol (1m) transitions cooperatively to an extended conformation (1w) resembling a cyclic b-hairpin; observation of an isodichroic point in the solvent-dependent CD spectra indicates that this transition is a two-state process. In contrast, neither 1m nor 1w show cooperative thermal melting; instead, theirstructures appear intact at temperatures as high as 65 8C; this observation suggests that steric constraint is dominant in stabilizing these structures. Finally, the 1H NMR CaH spectroscopic resonances of 1m are downfield-shifted with respect to random-coil values, a hitherto unreported property for b helices that appears to be a general feature of these structures. These results show for the first time that an appropriately designed b-helical peptide can fold stably in a polar solvent; furthermore, the structural and spectroscopic data reported should prove useful in the future design and characterization of water-soluble b helices.
机译：b螺旋-由交替的d，l-肽形成并通过b-sheet氢键稳定的螺旋-仅在少数高度疏水的肽中自然存在。本文通过介绍亲水性d，l-肽1（在甲醇中形成b螺旋）的第一个设计和生物物理特征，探索了b-螺旋结构的范围。 1的设计基于b-发夹/ b螺旋-一种新的超中学级化合物，以前仅针对非极性溶剂中的疏水性肽进行过表征。通过在CD分析超离心（AUC），NMR光谱和基于NMR的结构计算中证明，在1中掺入极性残基可提供在甲醇中的溶解度，其中该肽采用预期的b-发夹/螺旋结构。用水滴定（以恒定的肽浓度）后，甲醇（1m）中的结构协同转变为类似于环状b发夹的延伸构象（1w）。在溶剂依赖性CD光谱中观察到一个等分点，表明这种转变是一个两态过程。相反，无论是1m还是1w都没有表现出协同的热融解。相反，它们的结构在高达65 8C的温度下看起来完好无损;该观察结果表明，空间约束在稳定这些结构中占主导地位。最后，相对于随机线圈值，1m的1H NMR CaH光谱共振向低场偏移，这是迄今未报道的b螺旋性质，似乎是这些结构的普遍特征。这些结果首次表明，经过适当设计的β-螺旋肽可以在极性溶剂中稳定折叠。此外，所报道的结构和光谱数据应证明对水溶性双螺旋的未来设计和表征有用。

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