Frequency selective heteronuclear dipolar recoupling in rotating solids:: Accurate 13C-15N distance measurements in uniformly 13C,15N-labeled peptides
Frequency selective heteronuclear dipolar recoupling in rotating solids:: Accurate 13C-15N distance measurements in uniformly 13C,15N-labeled peptides
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DOI：
10.1021/ja003266e
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发表时间：
2001-04-18
影响因子：
15
通讯作者：
Griffin, RG
中科院分区：
文献类型：
--
作者：
Jaroniec, CP;Tounge, BA;Griffin, RG
我们描述了一个魔角旋转核磁共振实验，用于在均匀的C-13， n -15标记的固体中选择性测量C-13- n -15距离，其中多个C-13- n -15和C-13-C-13相互作用使结构上有趣的，弱C-13- n -15偶极耦合的精确测量复杂化。这项新实验被称为FSR (frequency selective REDOR)，将REDOR脉冲序列与频率选择性自旋回波相结合，在多自旋系统中重新耦合单个C-13-N-15偶极相互作用。同时，剩余的C-13- n -15偶极耦合和所有与所选C-13的C-13-C-13标量耦合被抑制。通过对实验观测到的C-13自旋回波强度调制的最小二乘拟合，提取了C-13- n- 15耦合，并将其拟合为描述孤立异核自旋对在常规REDOR下的偶极减相的解析表达式。实验在三种统一的C-13， n -15标记的模型体系中进行了验证：天冬酰胺，n -乙酰-l -缬氨酸-l -l -亮氨酸n -甲酰-l - met -l -亮氨酸-l -亮氨酸；在n -甲酰基-[U-C-13，N-15]L-Met-L-Leu-L-Phe中，我们在2.5-6埃范围内共确定了16个核间距离。
We describe a magic-angle spinning NMR experiment for selective C-13-N-15 distance measurements in uniformly C-13,N-15-labeled solids, where multiple C-13-N-15 and C-13-C-13 interactions complicate the accurate measurement of structurally interesting, weak C-13-N-15 dipolar couplings. The new experiment, termed FSR (frequency selective REDOR), combines the REDOR pulse sequence with a frequency selective spin-echo to recouple a single C-13-N-15 dipolar interaction in a multiple spin system. Concurrently the remaining C-13-N-15 dipolar couplings and all C-13-C-13 scalar couplings to the selected C-13 are suppressed. The C-13-N-15 coupling of interest is extracted by a least-squares fit of the experimentally observed modulation of the C-13 spin-echo intensity to the analytical expression describing the dipolar dephasing in an isolated heteronuclear spin pair under conventional REDOR. The experiment is demonstrated in three uniformly C-13,N-15-labeled model systems: asparagine, N-acetyl-L-Val-L-Leu acid N-formyl-L-Met-L-Leu-L-Phe; in N-formyl-[U-C-13,N-15]L-Met-L-Leu-L-Phe we have determined a total of 16 internuclear distances in the 2.5-6 Angstrom range.