Positional screening and NMR structure determination of side-chain-to-side-chain cyclized β<sup>3</sup>-peptides
作者:Esther Vaz、Sonja A. Dames、Matthias Geyer、Luc Brunsveld
DOI:10.1039/c1ob06422c
日期:——
Many β-peptides fold in a 14-helical secondary structure in organic solvents, but similar 14-helix formation in water requires additional stabilizing elements. Especially the 14-helix stabilization of short β-peptides in aqueous solution is critical, due to the limited freedom for incorporating stabilizing elements. Here we show how a single lactam bridge, connecting two β-amino acid side-chains, can lead to high 14-helix character in short β3-peptides in water. A comparative study, using CD and NMR spectroscopy and structure calculations, revealed the strong 14-helix inducing power of a side-chain-to-side-chain cyclization and its optimal position on the β3-peptide scaffold with respect to pH and ionic strength effects. The lactam bridge is ideally incorporated in the N-terminal region of the β3-peptide, where it limits the conformational flexibility of the peptide backbone. The lactam bridge induces a 14-helical conformation in methanol and water to a similar extent. Based on the presented first high resolution NMR 3D structure of a lactam bridged β3-peptide, the fold shows a large degree of high order, both in the backbone and in the side-chains, leading to a highly compact and stable folded structure.
许多β-肽在有机溶剂中折叠成14 螺旋二级结构,但在水中形成类似的14 螺旋需要额外的稳定元素。特别是短β-肽在水溶液中的14 螺旋稳定性至关重要,因为掺入稳定元素的自由度有限。在这里,我们展示了连接两个β-氨基酸侧链的单个内酰胺桥如何在水中产生短β3-肽的高14螺旋特征。使用 CD 和 NMR 光谱和结构计算进行的比较研究揭示了侧链到侧链环化的强大 14 螺旋诱导能力及其在 β3 肽支架上相对于 pH 和离子强度的最佳位置影响。内酰胺桥理想地结合在β3 肽的N 末端区域,在那里它限制了肽主链的构象灵活性。内酰胺桥在甲醇和水中诱导出类似程度的 14 螺旋构象。基于所提出的内酰胺桥β3 肽的第一个高分辨率NMR 3D 结构,折叠显示出很大程度的高有序性,无论是在主链还是在侧链中,导致高度紧凑和稳定的折叠结构。