Schubert Franziska, Pagel Kevin, Rossi Mariana, Warnke Stephan, Salwiczek Mario, Koksch Beate, von Helden Gert, Blum Volker, Baldauf Carsten, Scheffler Matthias
Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany.
Phys Chem Chem Phys. 2015 Feb 21;17(7):5376-85. doi: 10.1039/c4cp05216a.
In the natural peptides, helices are stabilized by hydrogen bonds that point backward along the sequence direction. Until now, there is only little evidence for the existence of analogous structures in oligomers of conformationally unrestricted β amino acids. We specifically designed the β peptide Ac-(β(2)hAla)6-LysH(+) to form native like helical structures in the gas phase. The design follows the known properties of the peptide Ac-Ala6-LysH(+) that forms a α helix in isolation. We perform ion-mobility mass-spectrometry and vibrational spectroscopy in the gas phase, combined with state-of-the-art density-functional theory simulations of these molecular systems in order to characterize their structure. We can show that the straightforward exchange of alanine residues for the homologous β amino acids generates a system that is generally capable of adopting native like helices with backward oriented H-bonds. By pushing the limits of theory and experiments, we show that one cannot assign a single preferred structure type due to the densely populated energy landscape and present an interpretation of the data that suggests an equilibrium of three helical structures.
在天然肽中，螺旋结构由沿着序列方向向后指向的氢键稳定。到目前为止，在构象不受限制的β氨基酸低聚物中，几乎没有证据表明存在类似结构。我们专门设计了β肽Ac-(β(2)hAla)6-LysH(+)，使其在气相中形成类似天然的螺旋结构。该设计遵循了肽Ac-Ala6-LysH(+)的已知特性，该肽单独形成α螺旋。我们在气相中进行离子迁移率质谱和振动光谱，并结合这些分子系统的最新密度泛函理论模拟，以表征它们的结构。我们可以证明，将丙氨酸残基直接替换为同源的β氨基酸会产生一个通常能够采用具有向后定向氢键的类似天然螺旋的系统。通过突破理论和实验的极限，我们表明由于能量景观密集，无法确定单一的优选结构类型，并对数据进行了解释，表明存在三种螺旋结构的平衡。
