Tjandra N, Bax A
Laboratory of Biophysical Chemistry, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-0380, USA.
Science. 1997 Nov 7;278(5340):1111-4. doi: 10.1126/science.278.5340.1111.
In isotropic solution, internuclear dipolar couplings average to zero as a result of rotational diffusion. By dissolving macromolecules in a dilute aqueous nematic discotic liquid-crystalline medium containing widely spaced magnetically oriented particles, a tunable degree of solute alignment with the magnetic field can be created while retaining the high resolution and sensitivity of the regular isotropic nuclear magnetic resonance (NMR) spectrum. Dipolar couplings between 1H-1H, 1H-13C, 1H-15N, and 13C-13C pairs in such an oriented macromolecule no longer average to zero, and are readily measured. Distances and angles derived from dipolar couplings in human ubiquitin are in excellent agreement with its crystal structure. The approach promises to improve the accuracy of structures determined by NMR, and extend the size limit.
在各向同性溶液中，由于旋转扩散，核间偶极耦合平均值为零。通过将大分子溶解在含有间隔较宽的磁性取向颗粒的稀水性向列型盘状液晶介质中，可以在保持常规各向同性核磁共振（NMR）谱的高分辨率和灵敏度的同时，产生与磁场可调谐的溶质取向程度。在这种取向的大分子中，1H-1H、1H-13C、1H-15N和13C-13C对之间的偶极耦合不再平均为零，并且易于测量。从人泛素中的偶极耦合得出的距离和角度与其晶体结构非常吻合。该方法有望提高通过核磁共振确定的结构的准确性，并扩大尺寸限制。
