Ultrahigh resolution in proton solid-state NMR spectroscopy at high levels of deuteration
Ultrahigh resolution in proton solid-state NMR spectroscopy at high levels of deuteration
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DOI：
10.1002/anie.200600328
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发表时间：
2006-01-01
影响因子：
16.6
通讯作者：
Reif, B
中科院分区：
文献类型：
--
作者：
Chevelkov, V;Rehbein, K;Reif, B
高分辨率魔角旋转（MAS）固态核磁共振光谱学的生物固体的结构研究在过去的几年中取得了迅速的进展，并导致了一些肽和小蛋白质的完整结构解析。[1-4]然而，成功的光谱分配和同位素富集材料（主要是13 C，15 N）的结构约束的确定仍然受到分辨率和灵敏度的限制。固态NMR（ssNMR）实验中的灵敏度的增益原则上可以使用直接质子检测来实现。该技术利用质子的高旋磁比g，然而，这一特性导致宽共振线。已经提出了几种方法来实现线窄化。应用加窗Homestructive去耦方案[5，6]产生了140- 400 Hz量级的重新缩放的1H线宽，但需要大的接收器带宽，这允许射频（RF）噪声折叠到频谱区域中，最终损害整体灵敏度。此外，所施加的脉冲序列缩放1H化学位移。近年来，高速（35-60 kHz）MAS仪器已变得可用。[7-9]然而，即使在这些高旋转速率下，完全质子化的样品仍然具有均匀加宽的谱线（> 500 Hz）。或者，在中等（10- 20 kHz）MAS频率下，通过同位素自旋稀释可以实现1H谱线窄化。[10-14]通过样品的全氘化和随后的质子对氘的反交换来实现稀释。在这些实验中，大多数共振的1H线宽通常在不存在和存在homopolymer 1H、1H去耦的情况下分别为150-250 Hz或80-150 Hz的量级。这种标记策略除了允许测定长程HN-HN距离外，还允许[12，15，16]检测蛋白质结构中的动态水分子[16，17]和表征蛋白质侧链动力学。[18，第19页]
Structure investigations of biological solids by high-resolution magic-angle spinning (MAS) solid-state NMR spectroscopy has rapidly progressed in the last few years and resulted in complete structure elucidation of several peptides and small proteins.[1–4] Successful spectral assignment and determination of structural constraints in isotopically enriched materials (mostly 13C, 15N) is, however, still limited by resolution and sensitivity. A gain in sensitivity in solid-state NMR (ssNMR) experiments can in principle be achieved using direct proton detection. This technique makes use of the high gyromagnetic ratio g of protons, a property which however, leads to broad resonance lines. Several approaches have been suggested to achieve line narrowing. Application of windowed homonuclear decoupling schemes [5, 6] yield a rescaled 1H line width on the order of 140–400Hz, but require large receiver bandwidths, which allows radio-frequency (RF) noise to fold into the spectral region which finally compromises overall sensitivity. In addition, the applied pulse sequences scale the 1H chemical shift. In recent years, high-speed (35–60 kHz) MAS instrumentation has become available.[7–9] However, even at these high spinning rates, fully protonated samples still have homogeneously broadened lines (> 500 Hz). Alternatively, 1H line narrowing could be achieved by isotopic spin dilution at moderate (10–20kHz) MAS frequencies.[10–14] Dilution is achieved by perdeuteration of the sample and subsequent back-exchange of deuterons by protons. In these experiments, the 1H line width of most of the resonances is typically on the order 150–250 Hz or 80–150 Hz in the absence and in the presence of homonuclear 1H, 1H decoupling, respectively. This labeling strategy allows, in addition the determination of long-range HN–HN distances,[12, 15, 16] detection of dynamic water molecules in the protein structure [16, 17] and the characterization of protein side-chain dynamics.[18, 19]