Dipole-dipole cross-correlated relaxation (CCR) between two spin pairs is rich with macromolecular structural and dynamic information on inter-nuclear bond vectors. Measurement of short range dipolar CCR rates has been demonstrated for a variety of inter-nuclear vector spin pairs in proteins and nucleic acids, where the multiple quantum coherence necessary for observing the CCR rate is created by through-bond scalar coupling. In principle, CCR rates can be measured for any pair of inter-nuclear vectors where coherence can be generated between one spin of each spin pair, regardless of both the distance between the two spin pairs and the distance of the two spins forming the multiple quantum coherence. In practice, however, long range CCR (lrCCR) rates are challenging to measure due to difficulties in linking spatially distant spin pairs. By utilizing through-space relaxation allowed coherence transfer (RACT), we have developed a new method for the measurement of lrCCR rates involving CαHα bonds on opposing anti-parallel β-strands. The resulting lrCCR rates are straightforward to interpret since only the angle between the two vectors modulates the strength of the interference effect. We applied our lrCCR measurement to the third immunoglobulin-binding domain of the streptococcal protein G (GB3) and utilize published NMR ensembles and static NMR/X-ray structures to highlight the relationship between the lrCCR rates and the CαHα-CαHα inter-bond angle and bond mobility. Furthermore, we employ the lrCCR rates to guide the selection of sub-ensembles from the published NMR ensembles for enhancing the structural and dynamic interpretation of the data. We foresee this methodology for measuring lrCCR rates as improving the generation of structural ensembles by providing highly accurate details concerning the orientation of CαHα bonds on opposing anti-parallel β-strands.

中文翻译：

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利用偶极-偶极交叉相关弛豫测量反平行 β 折叠中相对 CαHα-CαHα 键对之间的角度

两个自旋对之间的偶极-偶极交叉相关弛豫 (CCR) 富含有关核间键向量的大分子结构和动态信息。对于蛋白质和核酸中的各种核间矢量自旋对，短程偶极 CCR 率的测量已得到证明，其中观察 CCR 率所需的多量子相干性是通过键结标量耦合产生的。原则上，可以测量任何一对核间矢量的 CCR 率，其中每个自旋对的一个自旋之间可以产生相干性，而不管两个自旋对之间的距离和形成多量子的两个自旋的距离。连贯性。然而，在实践中，由于难以连接空间遥远的自旋对，远距离 CCR (lrCCR) 速率很难测量。通过利用空间弛豫允许相干转移 (RACT)，我们开发了一种测量 lrCCR 率的新方法，该方法涉及相对反平行 β 链上的 CαHα 键。由此产生的 lrCCR 率很容易解释，因为只有两个向量之间的角度会调节干扰效应的强度。我们将 lrCCR 测量应用于链球菌蛋白 G (GB3) 的第三个免疫球蛋白结合域，并利用已发表的 NMR 集合和静态 NMR/X 射线结构来突出 lrCCR 速率与 CαHα-CαHα 键间角之间的关系和债券流动性。此外，我们使用 lrCCR 率来指导从已发布的 NMR 集合中选择子集合，以增强数据的结构和动态解释。