Selective stable isotope labeling has transformed structural and dynamics analysis of RNA by NMR spectroscopy. These methods can remove ¹³C-¹³C dipolar couplings that complicate ¹³C relaxation analyses. While these phenomena are well documented for sites with adjacent ¹³C nuclei (e.g. ribose C1′), less is known about so-called isolated sites (e.g. adenosine C2). To investigate and quantify the effects of long-range (> 2 Å) ¹³C-¹³C dipolar interactions on RNA dynamics, we simulated adenosine C2 relaxation rates in uniformly [U-¹³C/¹⁵N]-ATP or selectively [2-¹³C]-ATP labeled RNAs. Our simulations predict non-negligible ¹³C-¹³C dipolar contributions from adenosine C4, C5, and C6 to C2 longitudinal (R₁) relaxation rates in [U-¹³C/¹⁵N]-ATP labeled RNAs. Moreover, these contributions increase at higher magnetic fields and molecular weights to introduce discrepancies that exceed 50%. This will become increasingly important at GHz fields. Experimental R₁ measurements in the 61 nucleotide human hepatitis B virus encapsidation signal ε RNA labeled with [U-¹³C/¹⁵N]-ATP or [2-¹³C]-ATP corroborate these simulations. Thus, in the absence of selectively labeled samples, long-range ¹³C-¹³C dipolar contributions must be explicitly taken into account when interpreting adenosine C2 R₁ rates in terms of motional models for large RNAs.

选择性稳定同位素标记改变了核磁共振光谱对 RNA 的结构和动力学分析。这些方法可以除去^13个C- ¹³那复杂Ç偶极联轴器¹³ ℃下的松弛分析。虽然这些现象在具有相邻¹³ C 核（例如核糖 C1'）的位点有详细记录，但对所谓的孤立位点（例如腺苷 C2）知之甚少。为了研究和量化长程 (> 2 Å) ¹³ C- ¹³ C 偶极相互作用对 RNA 动力学的影响，我们模拟了均匀 [U- ¹³ C/ ¹⁵ N]-ATP 或选择性 [2- ¹³C]-ATP 标记的 RNA。我们的模拟预测了 [U- ¹³ C/ ¹⁵ N]-ATP 标记的 RNA 中从腺苷 C4、C5 和 C6 到 C2 纵向 (R ₁ ) 弛豫率的不可忽略的¹³ C- ¹³ C 偶极贡献。此外，这些贡献在更高的磁场和分子量下增加，以引入超过 50% 的差异。这在 GHz 领域将变得越来越重要。实验- [R _1点的测量在61个核苷酸人乙型肝炎病毒壳体化信号εRNA标记有[U- ¹³ C / ¹⁵ N] -ATP或[2- ¹³C]-ATP 证实了这些模拟。因此，在没有选择性标记的样本的情况下，在根据大 RNA 的运动模型解释腺苷 C2 R ₁率时，必须明确考虑长程¹³ C- ¹³ C 偶极贡献。