HETERONUCLEAR SPIN DECOUPLING IN SOLID STATE NMR

固态核磁共振中的异核自旋解耦

• 批准号: 6279721
• 负责人: CHAD M RIENSTRA
• 金额: $ 0.71万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6279721
• 关键词: biomedical resource; proteins; technology /technique

Due to increased chemical shift offsets from resonance among abundant spins (usually 1H), decoupling becomes more demanding at high field. In addition, the high rates of MAS, required to average the anisotropic interactions, render the proton spin reservoir inhomogeneous. Under these conditions, the effects of insufficient decoupling become dramatic. The two-point phase-modulated (TPPM) decoupling sequence which we have developed demonstrates significant improvement over continuous-wave (CW) decoupling in inhomogeneous spin systems such as calcium 13C-formate, as well as more homogeneous cases such as ~-'3C. 5N-glycine. In inhomogeneous systems, the self-decoupling effect due to homonuclear couplings within the 1H reservoir is minimal, and so CW decoupling is particularly ineffective. The reduction of the second-order recoupling described by Ernst et al. is significant with TPPM. In u- 13C,1 5N-glycine, additional CW decoupling power improves resolution and sensitivity. However, even with improved probe technology, the contribution of strong dipolar couplings due to abundant 1H nuclei cannot be effectively removed with CW decoupling alone. Increasing from 75 kHz to 125 kHz CW decoupling provides an improvement in linewidth from 66 to 25 Hz, and an additional increase to tSO kHz provides additional signal intensity albeit without narrowing. The more dramatic improvement is observed when switching to the TPPM method; here a factor of six in narrowing and a factor of ten in sensitivity (peak height) is observed when comparing the 75 kHz CW decoupling and 12S kHz TPPM decoupling results. The combination of improved probe technology and decoupling methodology has potential to provide significant increases in the sensitivity and resolution of direct and indirect chemical shift dimensions. and the improvements in these categories expected at higher magnetic fields have been realized.

由于化学位移从共振中抵消的增加 自旋丰富(通常为1H)，高自旋时解耦要求更高 菲尔德。此外，MAS的高比率，需要平均 各向异性相互作用，使质子自旋库 不均匀的。在这种情况下，不充分的影响 脱钩变得戏剧性的。两点调相(TPPM) 我们开发的解耦序列具有重要的意义 对非均匀自旋连续波(CW)去耦合的改进 系统，如13C-甲酸钙，以及更均匀的情况 如~-‘3C.5N-甘氨酸。在非均相体系中， 1H内同核耦合的自去耦合效应 库存量最小，因此连续波解耦尤为重要 效果不佳。二阶重耦合的约化描述 作者：Ernst等人。对于TPPM来说意义重大。在u-13C中，15N-甘氨酸， 额外的连续波解耦能力提高了分辨率和灵敏度。 然而，即使有了改进的探测器技术， 由于丰富的1H核而产生的强偶极耦合不可能是 仅通过CW解耦即可有效消除。从75千赫增加 至125 kHz的CW去耦可将线宽从66 kHz提高到 到25赫兹，额外增加到Tso kHz可提供额外的 信号强度虽然没有变窄。越有戏剧性 当切换到TPPM方法时，可以观察到改进；在这里， 缩小为原来的6倍，灵敏度为原来的10倍(峰值 高度)，当比较75 kHz CW去耦合和12s时观察到 KHzTPPM解耦结果。改进型探头的组合 技术和解耦方法有可能提供 DIRECT和DIRECT的灵敏度和分辨率显著提高 间接化学位移维度。以及这些方面的改进 在较高磁场下预期的类别已经实现。