Multidimensional magic angle spinning NMR spectroscopy for site-resolved measurement of proton chemical shift anisotropy in biological solids.
Multidimensional magic angle spinning NMR spectroscopy for site-resolved measurement of proton chemical shift anisotropy in biological solids.
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DOI：
10.1021/ja3084972
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发表时间：
2013-01-30
影响因子：
15
通讯作者：
Vega, Alexander J.
中科院分区：
文献类型：
--
作者：
Hou, Guangjin;Paramasivam, Sivakumar;Yan, Si;Polenova, Tatyana;Vega, Alexander J.
质子化学位移(CS)张量是结构和氢键的灵敏探针。高精度的量子化学协议可以在不同的环境下计算1H的磁屏蔽，这使得质子化学位移有可能成为结构和电子性质的强大预测因子。然而，由于实验数据的匮乏，1H CS张量在蛋白质结构计算中的应用还不是很广泛。虽然即使在固体状态下也可以很容易地测量蛋白质的各向同性质子位移，但测定1H化学位移各向异性(CSA)张量仍然具有挑战性，特别是在含有多个质子中心的分子中。我们提出了一种在魔角旋转下测量完全质子化固体中酰胺质子CSA的位置分辨方法。该方法包括三个相伴的3D实验，产生的光谱要么主要由1H CSA，主要是1H-15N偶极相互作用确定，要么由1H CSA和1H-15N偶极相互作用相结合确定。各向异性相互作用使用适当对称性的RN序列重新耦合，并通过较短的选择性1H-15N交叉极化步长引入15N/13C各向同性CS维度。通过同时拟合三个光谱中记录的线型，提取了准确的~1H化学位移张量参数。给出了该方法在动力蛋白89个残基U-13C，15N-CAP-Gly结构域中的应用。由三重拟合法确定的CSA参数与氢键距离相关，其趋势与先前的溶液核磁共振结果非常一致。这种方法通常适合于记录各种生物和有机系统中的质子CSA参数，包括蛋白质组件和核酸。
The proton chemical shift (CS) tensor is a sensitive probe of structure and hydrogen bonding. Highly accurate quantum-chemical protocols exist for computation of 1H magnetic shieldings in the various contexts, making proton chemical shifts potentially a powerful predictor of structural and electronic properties. However, 1H CS tensors are not yet widely used in protein structure calculation due to scarcity of experimental data. While isotropic proton shifts can be readily measured in proteins even in the solid state, determination of the 1H chemical shift anisotropy (CSA) tensors remains challenging, particularly in molecules containing multiple proton sites. We present a method for site-resolved measurement of amide proton CSAs in fully protonated solids under magic angle spinning. The approach consists of three concomitant 3D experiments yielding spectra determined by either mainly 1H CSA, mainly 1H-15N dipolar, or combined 1H CSA and 1H-15N dipolar interactions. The anisotropic interactions are recoupled using RN-sequences of appropriate symmetry, such as , and 15N/13C isotropic CS dimensions are introduced via a short selective 1H-15N cross-polarization step. Accurate 1H chemical shift tensor parameters are extracted by simultaneous fit of the lineshapes recorded in the three spectra. An application of this method is presented for an 89-residue protein, U-13C,15N-CAP-Gly domain of dynactin. The CSA parameters determined from the triple fits correlate with the hydrogen-bonding distances, and the trends are in excellent agreement with the prior solution NMR results. This approach is generally suited for recording proton CSA parameters in various biological and organic systems, including protein assemblies and nucleic acids.
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