AUDIO-FREQUENCY NMR IN A NUTATING FRAME - APPLICATION TO THE ASSIGNMENT OF PHENYLALANINE RESIDUES IN ISOTOPICALLY ENRICHED PROTEINS
AUDIO-FREQUENCY NMR IN A NUTATING FRAME - APPLICATION TO THE ASSIGNMENT OF PHENYLALANINE RESIDUES IN ISOTOPICALLY ENRICHED PROTEINS
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DOI：
10.1021/ja00129a016
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发表时间：
1995-06-21
影响因子：
15
通讯作者：
BAX, A
中科院分区：
文献类型：
--
作者：
GRZESIEK, S;BAX, A
化学位移的影响可以通过沿着强射频场量子化核自旋并施加与有效射频自旋锁定场方向正交的第二音频磁场来消除到高阶。通过将该第二磁场的音频调制频率调整为自旋绕RF场旋转的速率，建立了自旋锁定框架中的共振条件，该条件在二阶上与同核自旋的共振偏移无关。音频场的相位和幅值由操作员控制，使得在张动帧中进行复杂的脉冲序列成为可能。该方法证明了在一个单一的磁化从苯丙氨酸C-13（β）转移到所有芳香环碳在一个均匀的C-13富集钙调素样品。该实验的三维版本为结构信息丰富的芳香Phe信号提供了完整的共振分配，包括所有C-13（zeta）和H-1（zeta）共振。
The effect of chemical shift can be removed to high order by quantizing nuclear spins along a strong radio-frequency (RF) field and applying a second audio-frequency magnetic field, orthogonal to the direction of the effective RF spin lock field. By adjusting the audio-modulation frequency of this second magnetic field to the rate at which spins nutate about the RF field, a resonance condition in the spin-locked frame is established which, to second order, is independent of the resonance offset of the homonuclear spins. The phase and amplitude of the audio-frequency field are under operator control and make it possible to conduct complex pulse sequences in the nutating frame. The approach is demonstrated for transferring in a single step magnetization from phenylalanine C-13(beta) to all aromatic ring carbons in a sample of uniformly C-13-enriched calmodulin. A three-dimensional version of the experiment yields complete resonance assignments for the structurally informative aromatic Phe signals, including all C-13(zeta) and H-1(zeta) resonances.