Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot 7610001, Israel.
Department of Physics, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547, Kerala, India.
J Am Chem Soc. 2021 Apr 7;143(13):4942-4948. doi: 10.1021/jacs.1c01914. Epub 2021 Mar 30.
Multidimensional NOESY experiments targeting correlations between exchangeable imino and amino protons provide valuable information about base pairing in nucleic acids. It has been recently shown that the sensitivity of homonuclear correlations involving RNA's labile imino protons can be significantly enhanced, by exploiting the repolarization brought about by solvent exchanges. Homonuclear correlations, however, are of limited spectral resolution, and usually incapable of tackling relatively large homopolymers with repeating structures like RNAs. This study presents a heteronuclear-resolved version of those NOESY experiments, in which magnetization transfers between the aqueous solvent and the nucleic acid protons are controlled by selecting specific chemical shift combinations of a coupled H-N spin pair. This selective control effectively leads to a pseudo-3D version of HSQC-NOESY, but with cross-peaks enhanced by ∼2-5× as compared with conventional 2D NOESY counterparts. The enhanced signal sensitivity as well as access to both N-H and H-H NOESY dimensions can greatly facilitate RNA assignments and secondary structure determinations, as demonstrated here with the analysis of genome fragments derived from the SARS-CoV-2 virus.
多维 NOESY 实验针对可交换亚氨基和氨基质子之间的相关联，提供了有关核酸碱基配对的有价值的信息。最近已经表明，通过利用溶剂交换带来的再极化，可以显著提高涉及 RNA 不稳定亚氨基质子的同核相关的灵敏度。然而，同核相关的谱分辨率有限，通常无法解决具有重复结构的相对较大的均聚物，如 RNA。本研究提出了这些 NOESY 实验的异核分辨版本，其中通过选择耦合 H-N 自旋对的特定化学位移组合来控制水溶剂和核酸质子之间的磁化转移。这种选择性控制有效地导致了 HSQC-NOESY 的伪 3D 版本，但与传统的 2D NOESY 对应物相比，交叉峰增强了 2-5 倍。增强的信号灵敏度以及对 N-H 和 H-H NOESY 维度的访问，可以极大地促进 RNA 分配和二级结构的确定，如这里使用 SARS-CoV-2 病毒衍生的基因组片段的分析所证明的那样。
