Abstract
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 13C or 15N with lower gyromagnetic ratio than 1H) 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 1H coherences, detected by 13C NMR spectroscopy. Furthermore, 13C and 15N chemical shifts provide valuable information on conformations. All the covered aspects point to the advantages of low‐γ nuclei detection experiments in RNA.
Highlights
Since the development of multidimensional NMR spectroscopy and the availability of isotope-labeled Ribonucleic acid oligonucleotides (RNAs), NMR spectroscopy has contributed more than 40 % of all RNA structures in databases
To describe and understand this functional diversity, structural studies of RNA are increasingly important. 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
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-g nuclei to obtain unique structural and dynamic information for large RNA molecules in solution
Summary
Since the development of multidimensional NMR spectroscopy and the availability of isotope-labeled RNAs, NMR spectroscopy has contributed more than 40 % of all RNA structures in databases. The disadvantage due to low-g detection can be minimized thanks to new cryogenic probes with inner NMR coils optimized for 13C-, 19F-, or 15N-detection.[14] despite their lower fundamental signalto-noise ratio, heteronuclear-detection schemes have become feasible These heteronuclear-detected experiments benefit from the larger chemical shift dispersion, coupled to sharper line widths of the heteronuclei. The heteroaromatic nucleobases represent a cyclized chain of CÀN fragments This particular feature can be exploited for the direct magnetization transfer in NMR experiments in (multiple) INEPT steps without being dependent on 1H-excitation or Robbin Schnieders, born in 1991, studied chemistry at the University of Frankfurt and finished studying in 2016 with her master’s degree. Decoupling schemes like IP/AP[16] and S3E[17] as well as selective homonuclear decoupling during acquisition are available
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