The construction of complex protein folds relies on the precise conversion of a linear polypeptide chain into a compact 3-dimensional structure. In this context, study of isolated secondary structural modules containing short stretches of amino acids assumes significance. Additionally, peptides, both natural and synthetic, play a major role as potential drugs. With a view to understand the local conformations adopted by peptides in the solid state, we propose a multinuclear NMR approach utilizing spectra of nuclei in their natural isotopic abundance. Various solid-state NMR experiments have been utilized for assignment of the spectra. Additionally, the gauge-including projector augmented-wave (GIPAW) calculations were used to confirm the assignments. Particularly, the utility of the double-quantum-single-quantum correlation experiments is highlighted for the purpose of assignment and for inferring the conformation across the peptide bond. The methodology is illustrated for the case of designed peptides containing diproline residues occurring at the β-turns for identifying their cis-trans conformational polymorphism. The proposed method promises to be of use in the study of conformations of small- to medium-sized peptides such as antimicrobial peptides and in the study of polymorphism leading to applications in drug development protocols.

中文翻译：

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使用固态NMR光谱对肽进行构象研究-包含双脯氨酸的β-turn肽多态性研究。

复杂蛋白质折叠的构建依赖于线性多肽链向紧凑的3维结构的精确转化。在这种情况下，研究包含短片段氨基酸的分离的二级结构模块具有重要意义。另外，天然和合成的肽作为潜在药物也起主要作用。为了了解固态肽所采用的局部构象，我们提出了一种利用核在其天然同位素丰度中的光谱的多核NMR方法。各种固态NMR实验已用于光谱分配。此外，还使用了包含投影仪的增强波（GIPAW）的量规计算来确认分配。特别，为了分配和推断肽键上的构象，强调了双量子-单量子相关实验的实用性。针对所设计的肽的情况说明了该方法，所设计的肽包含在β-转位出现的双脯氨酸残基，用于鉴定其顺反构象多态性。所提出的方法有望用于研究中小型肽（如抗菌肽）的构象，以及用于导致药物开发方案中应用的多态性研究。