Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems
Recoupling of chemical shift anisotropies in solid-state NMR under high-speed magic-angle spinning and in uniformly 13C-labeled systems
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DOI：
10.1063/1.1565109
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发表时间：
2003-05-08
影响因子：
4.4
通讯作者：
Tycko, R
中科院分区：
文献类型：
--
作者：
Chan, JCC;Tycko, R
我们证明了在高速魔角旋转（MAS）下，在固态核磁共振（NMR）中重新耦合化学位移各向异性（CSA）相互作用的可能性，同时保持静态CSA粉末图案线形，并同时衰减同向偶极-偶极相互作用。CSA再耦合是通过旋转同步的射频脉冲序列与对称性，允许静态CSA线的形状，以获得。我们提出了一个特定的再耦合序列，我们称之为ROCSA，CSA和homopoly偶极-偶极相互作用的标度因子分别为0.272和约0.05。该序列适用于对均匀C-13标记的有机化合物（包括生物聚合物）进行高速C-13 MAS NMR实验。我们通过测量均匀标记的多晶化合物L-丙氨酸和N-乙酰基-D，L-缬氨酸在11和20 kHz的MAS频率下的C-13 CSA图案，实验证明了ROCSA序列。我们还提出了由与阿尔茨海默病相关的β-淀粉样蛋白肽的15个残基片段形成的淀粉样蛋白原纤维的实验数据，其中4个氨基酸残基被均匀地标记，证明了对高分子量和显着复杂性的生化系统的适用性。淀粉样蛋白原纤维样品中CSA模式的分析表明，ROCSA测量作为非结晶固体中肽和蛋白质构象的探针的实用性。(C)2003年，美国物理学会。
We demonstrate the possibility of recoupling chemical shift anisotropy (CSA) interactions in solid-state nuclear magnetic resonance (NMR) under high-speed magic-angle spinning (MAS) while retaining a static CSA powder pattern line shape and simultaneously attenuating homonuclear dipole-dipole interactions. CSA recoupling is accomplished by a rotation-synchronized radio-frequency pulse sequence with symmetry properties that permit static CSA line shapes to be obtained. We suggest a specific recoupling sequence, which we call ROCSA, for which the scaling factors for CSA and homonuclear dipole-dipole interactions are 0.272 and approximately 0.05, respectively. This sequence is suitable for high-speed C-13 MAS NMR experiments on uniformly C-13-labeled organic compounds, including biopolymers. We demonstrate the ROCSA sequence experimentally by measuring the C-13 CSA patterns of the uniformly labeled, polycrystalline compounds L-alanine and N-acetyl-D,L-valine at MAS frequencies of 11 and 20 kHz. We also present experimental data for amyloid fibrils formed by a 15-residue fragment of the beta-amyloid peptide associated with Alzheimer's disease, in which four amino acid residues are uniformly labeled, demonstrating the applicability to biochemical systems of high molecular weight and significant complexity. Analysis of the CSA patterns in the amyloid fibril sample demonstrates the utility of ROCSA measurements as probes of peptide and protein conformation in noncrystalline solids. (C) 2003 American Institute of Physics.