Tycko R
Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Health, Bethesda, MD 20892-0520, USA.
J Biomol NMR. 1996 Oct;8(3):239-51. doi: 10.1007/BF00410323.
The feasibility of assigning the backbone 15N and 13C NMR chemical shifts in multidimensional magic angle spinning NMR spectra of uniformly isotopically labeled proteins and peptides in unoriented solid samples is assessed by means of numerical simulations. The goal of these simulations is to examine how the upper limit on the size of a peptide for which unique assignments can be made depends on the spectral resolution, i.e., the NMR line widths. Sets of simulated three-dimensional chemical shift correlation spectra for artificial peptides of varying length are constructed from published liquid-state NMR chemical shift data for ubiquitin, a well-characterized soluble protein. Resonance assignments consistent with these spectra to within the assumed spectral resolution are found by a numerical search algorithm. The dependence of the number of consistent assignments on the assumed spectral resolution and on the length of the peptide is reported. If only three-dimensional chemical shift correlation data for backbone 15N and 13C nuclei are used, no residue-specific chemical shift information, information from amino acid side-chain signals, and proton chemical shift information are available, a spectral resolution of 1 ppm or less is generally required for a unique assignment of backbone chemical shifts for a peptide of 30 amino acid residues.
通过数值模拟评估了在未取向固体样品中对均匀同位素标记的蛋白质和肽进行多维魔角旋转核磁共振谱中主链15N和13C核磁共振化学位移归属的可行性。这些模拟的目的是研究能够进行唯一归属的肽大小上限如何取决于光谱分辨率，即核磁共振线宽。利用已发表的关于泛素（一种特征明确的可溶性蛋白质）的液态核磁共振化学位移数据，构建了不同长度人工肽的模拟三维化学位移相关谱集。通过数值搜索算法找到与这些谱在假定光谱分辨率范围内一致的共振归属。报告了一致归属数量对假定光谱分辨率和肽长度的依赖性。如果仅使用主链15N和13C核的三维化学位移相关数据，没有残基特异性化学位移信息、来自氨基酸侧链信号的信息以及质子化学位移信息，对于一个30个氨基酸残基的肽，通常需要1 ppm或更低 的光谱分辨率才能对主链化学位移进行唯一归属。
