Institute for Organic Chemistry and Chemical Biology, Center for Biomolecular Magnetic Resonance (BMRZ), Johann Wolfgang Goethe-Universität Frankfurt, Max-von-Laue-Str. 7, 60438, Frankfurt, Germany.
Chemistry. 2020 Jan 2;26(1):102-113. doi: 10.1002/chem.201903355. Epub 2019 Oct 22.
Ribonucleic acid oligonucleotides (RNAs) play pivotal roles in cellular function (riboswitches), chemical biology applications (SELEX-derived aptamers), cell biology and biomedical applications (transcriptomics). Furthermore, a growing number of RNA forms (long non-coding RNAs, circular RNAs) but also RNA modifications are identified, showing the ever increasing functional diversity of RNAs. To describe and understand this functional diversity, structural studies of RNA are increasingly important. However, they are often more challenging than protein structural studies as RNAs are substantially more dynamic and their function is often linked to their structural transitions between alternative conformations. NMR is a prime technique to characterize these structural dynamics with atomic resolution. To extend the NMR size limitation and to characterize large RNAs and their complexes above 200 nucleotides, new NMR techniques have been developed. This Minireview reports on the development of NMR methods that utilize detection on low-γ nuclei (heteronuclei like C or N with lower gyromagnetic ratio than H) to obtain unique structural and dynamic information for large RNA molecules in solution. Experiments involve through-bond correlations of nucleobases and the phosphodiester backbone of RNA for chemical shift assignment and make information on hydrogen bonding uniquely accessible. Previously unobservable NMR resonances of amino groups in RNA nucleobases are now detected in experiments involving conformational exchange-resistant double-quantum H coherences, detected by C NMR spectroscopy. Furthermore, C and N chemical shifts provide valuable information on conformations. All the covered aspects point to the advantages of low-γ nuclei detection experiments in RNA.
核糖核酸寡核苷酸（RNAs）在细胞功能（核酶）、化学生物学应用（SELEX 衍生的适体）、细胞生物学和生物医学应用（转录组学）中发挥着关键作用。此外，越来越多的 RNA 形式（长非编码 RNA、环状 RNA）以及 RNA 修饰被鉴定出来，显示出 RNA 的功能多样性不断增加。为了描述和理解这种功能多样性，对 RNA 的结构研究变得越来越重要。然而，与蛋白质结构研究相比，它们通常更具挑战性，因为 RNA 具有更大的动态性，其功能通常与其在不同构象之间的结构转变相关。NMR 是一种以原子分辨率描述这些结构动力学的主要技术。为了扩展 NMR 的尺寸限制并表征超过 200 个核苷酸的大 RNA 及其复合物，已经开发了新的 NMR 技术。这篇综述报告了利用检测低γ核（如 C 或 N 等比 H 更低的磁旋比核）的 NMR 方法的发展，以获得溶液中大 RNA 分子的独特结构和动态信息。实验涉及核碱基和 RNA 磷酸二酯骨架的键间相关，用于化学位移分配，并使氢键信息唯一可访问。以前在涉及构象交换抗性双量子 H 相干的实验中无法检测到的 RNA 碱基中的氨基的 NMR 共振现在可以被检测到，这是通过 C NMR 光谱实现的。此外，C 和 N 化学位移提供了关于构象的有价值的信息。所有涵盖的方面都指向了低γ核检测实验在 RNA 中的优势。
