Novel peptide foldameric motifs: a step forward in our understanding of the fully-extended conformation/310-helix coexistence
作者:Fernando Formaggio、Marco Crisma、Gema Ballano、Cristina Peggion、Mariano Venanzi、Claudio Toniolo
DOI:10.1039/c2ob06863j
日期:——
The fully-extended, multiple C5, conformation or 2.05 helix is a very appealing peptide secondary structure, in particular for its potential use as a molecular spacer, as it is characterized by the longest elevation (as high as 3.62 Å) between the α-carbon atoms of two consecutive α-amino acids. Despite this intriguing property, however, it is only poorly investigated and understood. Here, using a complete series of Cα,α-diethylglycine (Deg) homo-oligopeptide esters to the pentamer level, we exploited the properties of a fluorophore and a quencher, synthetically positioned at the N- and C-termini of the main chain, respectively, to check the applicability of the fully-extended conformation as a rigid molecular spacer. The fluorescence study was complemented by FT-IR absorption and NMR conformational investigations. The X-ray diffraction structures of selected compounds are also reported. Unfortunately, we find that, even in a solvent of low polarity, such as chloroform, in this peptide series an equilibrium does take place between the fragile fully-extended conformation and the 310-helical structure, the latter becoming more and more stable as the main chain is elongated. Since the Deg homo-peptide esters lacking any terminal aromatic group, previously investigated, are known to adopt a stable fully-extended conformation in chloroform solution, we tend to attribute the 3D-structure instability observed in this work to the presence of multiple aromatic rings in their blocking groups.
完全延伸的多重 C5 构象或 2.05 螺旋是一种非常有吸引力的肽二级结构,特别是其作为分子间隔物的潜在用途,因为它的特点是 α- 之间的最长海拔(高达 3.62 Å)两个连续的α-氨基酸的碳原子。然而,尽管有这种有趣的特性,但人们对它的研究和理解却很少。在这里,我们使用全系列的五聚体水平的 Cα,α-二乙基甘氨酸 (Deg) 同源寡肽酯,利用合成位于主链 N 和 C 末端的荧光团和猝灭剂的特性,分别检查完全延伸构象作为刚性分子间隔物的适用性。荧光研究得到 FT-IR 吸收和 NMR 构象研究的补充。还报道了所选化合物的 X 射线衍射结构。不幸的是,我们发现,即使在低极性溶剂(例如氯仿)中,在该肽系列中,脆弱的完全伸展构象和 310 螺旋结构之间确实会发生平衡,后者随着主链拉长。由于先前研究的缺乏任何末端芳香基团的 Deg 同肽酯已知在氯仿溶液中采用稳定的完全延伸构象,因此我们倾向于将本工作中观察到的 3D 结构不稳定性归因于多个芳香环的存在在他们的封锁组中。