NH NH VECTOR CORRELATION IN PEPTIDES BY SOLID STATE NMR

我们提出了一种新的固态核磁共振脉冲序列来测量 魔角旋转下的多肽投影角 (毫秒)。将该方法应用于均匀标记的15N- 三肽N-甲酰-MLF。测量的角度直接关系到 主干角0和W。同样的实验可以用来 抑制侧链扭转角，例如在“N-标记精氨酸”中 较大的自旋系统，投影角允许确定 不同次级结构元素之间的几何关系。这个 方法依赖于NH偶极耦合的重新耦合，这是 用质子介导的自旋与最近邻关联 扩散。异核相互作用用新的 异核重联方案T-MREV。与之相对的是 传统的MREV-8，异核偶极相互作用不是 在每个转子周期后重新聚焦。这扩展了的动态范围 并允许更准确地测定R值。 电子耦合交互。此外，我们在这里介绍了一种方法 以准解析的方式解释退相数据 允许高效提取分子参数。了解以下内容 序列的比例因子对于 数据的理论描述。

We present a novel solid-state NMR pulse sequence to measure the NHi-NHi,, projection angle in peptides under magic angle spinning (MAS). The method is applied to the uniformly 15 N-labelled tripeptide N-Formyl-MLF. The measured angle is directly related to the backbone angles 0 and W. The same experiment can be used to restrain side chain torsion angles, e.g. in "N-labelled arginine. In larger spin systems, the projection angle permits the determination of the geometry between different secondary structure elements. The method relies on the recoupling of the NH dipolar coupling, which is correlated to the nearest neighbor using proton mediated spin diffusion. The heteronuclear interaction is recoupled using the new heteronuclear recoupling scheme T-MREV. In contrast to the conventional MREV-8, the heteronuclear dipolar interaction is not refocussed after each rotor period. This extends the dynamic range of the experiment and allows for a more accurated determinatio n of the r ecoupled interaction. Furthermore, we present here an approach to interpret the dephasing data in a quasi-analytical fashion that permits efficient extraction of molecular parameters. Knowledge of the scaling factor of the sequence is not necessary for the theoretical description of the data.