13C-13C dipolar recoupling under very fast magic angle spinning in solid-state nuclear magnetic resonance:: Applications to distance measurements, spectral assignments, and high-throughput secondary-structure determination
13C-13C dipolar recoupling under very fast magic angle spinning in solid-state nuclear magnetic resonance:: Applications to distance measurements, spectral assignments, and high-throughput secondary-structure determination
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DOI：
10.1063/1.1359445
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发表时间：
2001-05-15
影响因子：
4.4
通讯作者：
Ishii, Y
中科院分区：
文献类型：
--
作者：
Ishii, Y
提出了一种在固体核磁共振谱中快速魔角旋转（MAS）条件下重耦合稀自旋对（如C-13-C-13体系）间均质偶极耦合的方法。所提出的技术，有限脉冲射频驱动的再耦合（fpRFDR），恢复homomandic偶极相互作用的基础上建设性地使用有限的脉冲宽度的影响，在相位和相位周期的π脉冲序列，其中转子同步π脉冲施加每个旋转周期。恢复的有效偶极相互作用具有静态固体的零量子偶极哈密顿量的形式，其在自旋空间中的对称性不同于通过常规的射频驱动再耦合（RFDR）技术获得的对称性。它表明，fpRFDR的再耦合的效率是不是强烈依赖于化学位移的差异或共振偏移在非常快的MAS下，以前的再耦合方法相反。为了实现无自旋弛豫影响的距离测量，提出了一种恒时型fpRFDR（CT-fpRFDR），该方法通过使用转子同步固体回波重聚焦偶极演化来改变有效演化周期，同时保持总的重耦合周期不变.从在17.6T的场中以30.3kHz的旋转速度的CT-fpRFDR实验，[1-C-13]Ala-[1-C-13]Gly-Gly的C-13-C-13距离被确定为3.27 A，这与通过X射线衍射获得的3.20埃的值很好地一致。此外，对于片段性C-13和N-15标记的阿尔茨海默氏β-淀粉样蛋白片段的原纤维，用fpRFDR获得9.4T场中的二维（2D）C-13/C-13化学位移相关NMR谱，A β（16-22）（残基16-22取自40个残基的A β肽），其中Leu-17至Ala-21均被C-13和N-15标记。主链和侧链的大多数C-13共振是基于特定于氨基酸类型的2D C-13/C-13化学位移相关模式分配的。对获得的C-13化学位移的检查揭示了在A β的整个分子中形成β链（16-22）。基于C-13位移的全球主链结构的高通量测定的可能性也讨论了均匀/分段C-13标记的蛋白质/肽样品的2D C-13/C-13化学位移相关性下非常快的MAS。
A technique is presented to recouple homonuclear dipolar couplings between dilute spin pairs such as C-13-C-13 systems under very fast magic angle spinning (MAS) in solid-state nuclear magnetic resonance (NMR) spectroscopy. The presented technique, finite pulse rf driven recoupling (fpRFDR), restores homonuclear dipolar interactions based on constructive usage of finite pulse-width effects in a phase- and symmetry-cycled pi -pulse train in which a rotor-synchronous pi pulse is applied every rotation period. The restored effective dipolar interaction has the form of a zero-quantum dipolar Hamiltonian for static solids, whose symmetry in spin space is different from that obtained by conventional rf driven recoupling (RFDR) techniques. It is demonstrated that the efficiency of recoupling by fpRFDR is not strongly dependent on chemical shift differences or resonance offsets in contrast to previous recoupling methods under very fast MAS. To realize distance measurements without effects of spin relaxation, a constant-time version of fpRFDR (CT-fpRFDR) is introduced, in which the effective evolution period is varied by refocusing dipolar evolution with a rotor-synchronized solid echo while the total recoupling period is kept constant. From CT-fpRFDR experiments at a spinning speed of 30.3 kHz in a field of 17.6 T, the C-13-C-13 distance of [1-C-13]Ala-[1-C-13]Gly-Gly was determined to be 3.27 A, which agrees well with the value of 3.20 Angstrom obtained by x-ray diffraction. Also, two-dimensional (2D) C-13/C-13 chemical-shift correlation NMR spectrum in a field of 9.4 T was obtained with fpRFDR for fibrils of the segmentally C-13- and N-15-labeled Alzheimer's beta -Amyloid fragments, A beta (16-22) (residues 16-22 taken from the 40-residue A beta peptide) in which Leu-17 through Ala-21 are uniformly C-13- and N-15-labeled. Most C-13 resonances for the main chain as well as for the side chains are assigned based on 2D C-13/C-13 chemical-shift correlation patterns specific to amino-acid types. Examination of the obtained C-13 chemical shifts revealed the formation of beta -strand across the entire molecule of A beta (16-22). Possibility of high throughput determination of global main-chain structures based on C-13 shifts obtained from 2D C-13/C-13 chemical-shift correlation under very fast MAS is also discussed for uniformly/segmentally C-13-labeled protein/peptide samples.