Quantitative Analysis of Solid-State Homonuclear Correlation Spectra of Antiparallel beta-Sheet Alanine Tetramers
Quantitative Analysis of Solid-State Homonuclear Correlation Spectra of Antiparallel beta-Sheet Alanine Tetramers
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反平行β-片丙氨酸四聚体的固态同核相关谱的定量分析
DOI：
10.1021/acs.jpcb.7b11126
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发表时间：
2018
期刊：
影响因子：
3.3
通讯作者：
and T. Asakura
中科院分区：
文献类型：
--
作者：
A. Naito;K. Okushita;K. Nishimura;G. S. Boutis;A. Aoki;and T. Asakura
聚-L-丙氨酸（PLA）序列是蜘蛛拖丝、野蚕丝、抗冻蛋白和淀粉样蛋白的晶体结构域的结构中的关键元件。迄今为止，没有原子级结构的反平行（AP）-PLA长于Ala 4已使用单晶X射线衍射分析报告。本文采用偶极辅助旋转共振固体核磁共振（Dipolar-assisted rotational resonance solid NMR）方法测定了13 C均匀标记的具有反平行β折叠结构的丙氨酸四聚体的有效核间距，其原子坐标由X射线晶体学分析确定。通过考虑主方程中产生的核间距，从交叉峰的积聚曲线获得初始积聚速率Rj，k。随后，实验获得的有效的核间距，reffj，k（obs），进行了比较与计算reffj，k（calc）从X射线晶体学数据获得的值。在不考虑零量子线形函数的情况下，在1.0-6.0 μ m范围内，reffj，k（obs）和reffj，k（calc）之间有很好的相关性，标准偏差为0.244 μ m.进一步指出，分子间贡献的核间距提供了与固态样品中分子堆积有关的细节。因此，目前的数据与AP-β-折叠堆积一致，但与P-β-折叠堆积不一致。
Poly-l-alanine (PLA) sequences are a key element in the structure of the crystalline domains of spider dragline silks, wild silkworm silks, antifreeze proteins, and amyloids. To date, no atomic-level structures of antiparallel (AP)-PLA longer than Ala4have been reported using the single-crystal X-ray diffraction analysis. In this work, dipolar-assisted rotational resonance solid-state NMR spectra were observed to determine the effective internuclear distances of13C uniformly labeled alanine tetramer with antiparallel (AP) β-sheet structure whose atomic coordinates are determined from the X-ray crystallographic analysis. Initial build-up rates,Rj,k, were obtained from the build-up curves of the cross peaks by considering the internuclear distances arising in the master equation. Subsequently, experimentally obtained effective internuclear distances,reffj,k(obs), were compared with the calculatedreffj,k(calc) values obtained from the X-ray crystallographic data. Fairly good correlation betweenreffj,k(obs) andreffj,k(calc) was obtained in the range of 1.0–6.0 Å, with the standard deviation of 0.244 Å, without considering the zero-quantum line-shape functions. It was further noted that the internuclear distances of intermolecular contributions provide details relating to the molecular packing in solid-state samples. Thus, the present data agree well with AP-β-sheet packing but do not agree with P-β-sheet packing.