Department of Chemistry, Indian Institute of Science Education and Research, Dr. Homi Bhabha Road, Pashan, Pune 411008, India.
Department of Chemistry, North Eastern Hill University, Shillong, Meghalaya 793022, India.
J Chem Phys. 2019 Sep 14;151(10):104309. doi: 10.1063/1.5115040.
Specific folded structures of peptides and proteins depend on the sequence of various amino acid residues as well as different types of noncovalent interactions induced by the backbone as well as side-chains of those residues. In general, secondary structures of peptides and proteins are stabilized by C6 (δ-turn), C7 (γ-turn), C10 (β-turn), C13 (α-turn), and C15 (π-turn) hydrogen-bonded rings formed through inter-residue interactions. However, it has been reported recently that an intraresidue C5 hydrogen-bond, which is relatively weak in strength, can contribute significantly to the stability of peptides and proteins. The C5 hydrogen-bond is mostly present in the β-sheet structures of peptides and proteins along with other inter-residue noncovalent interactions. In this work, we have studied structures and conformational preferences of a dipeptide Z-Gly-Pro-OH (Z = benzyloxycarbonyl) using mass-selected vibrationally resolved electronic spectroscopy and IR-UV double resonance spectroscopy coupled with quantum chemistry calculations. Two conformers of the peptide are observed in the experiment. One of the conformers has an extended β-strand type structure stabilized by C5 hydrogen-bonding, while the other one is folded through O-H ⋯ π interaction. The noncovalent interactions present in the two observed structures of the peptide are validated by natural bond orbital and noncovalent interaction calculations.
特定的肽和蛋白质折叠结构取决于各种氨基酸残基的序列以及由这些残基的主链和侧链诱导的不同类型的非共价相互作用。一般来说，肽和蛋白质的二级结构通过通过残基间相互作用形成的 C6（δ-转角）、C7（γ-转角）、C10（β-转角）、C13（α-转角）和 C15（π-转角）氢键环来稳定。然而，最近有报道称，强度相对较弱的 C5 氢键可以显著促进肽和蛋白质的稳定性。C5 氢键主要存在于肽和蛋白质的β-折叠结构中，以及其他残基间的非共价相互作用中。在这项工作中，我们使用质量选择的振动分辨电子光谱和 IR-UV 双共振光谱结合量子化学计算研究了二肽 Z-Gly-Pro-OH（Z = 苄氧羰基）的结构和构象偏好。实验中观察到该肽的两种构象。其中一种构象通过 C5 氢键稳定，具有伸展的 β-链型结构，而另一种则通过 O-H ⋯ π 相互作用折叠。通过自然键轨道和非共价相互作用计算验证了肽的两种观察到的结构中存在的非共价相互作用。
