Ketchem R R, Lee K C, Huo S, Cross T A
Center for Interdisciplinary Magnetic Resonance, Institute of Molecular Biophysics, Tallahassee, FL, USA.
J Biomol NMR. 1996 Jul;8(1):1-14. doi: 10.1007/BF00198135.
The complete structure determination of a polypeptide in a lipid bilayer environment is demonstrated built solely upon orientational constraints derived from solid-state NMR observations. Such constraints are obtained from isotopically labeled samples uniformly aligned with respect to the B(0) field. Each observation constrains the molecular frame with respect to B(0) and the bilayer normal, which are arranged to be parallel. These constraints are not only very precise ( a few tenths of a degree), but also very accurate. This is clearly demonstrated as the backbone structure is assembled sequentially and the i to i + 6 hydrogen bonds in this structure of the gramicidin channel are shown on average to be within 0.5 A of ideal geometry. Similarly, the side chains are assembled independently and in a radial direction from the backbone. The lack of considerable atomic overlap between side chains also demonstrates the accuracy of the constraints. Through this complete structure, solid-state NMR is demonstrated as an approach for determining three-dimensional macromolecular structure.
在脂质双层环境中多肽完整结构的测定仅基于从固态核磁共振观测中获得的取向约束得到了证明。这些约束来自相对于B(0)场均匀排列的同位素标记样品。每次观测都相对于B(0)和双层法线（二者排列为平行）约束分子框架。这些约束不仅非常精确（精确到十分之几度），而且非常准确。这在依次组装主链结构时得到了清楚的证明，并且短杆菌肽通道结构中的i到i + 6氢键平均显示在理想几何结构的0.5 Å范围内。同样，侧链是独立组装的，并且从主链沿径向排列。侧链之间缺乏大量原子重叠也证明了约束的准确性。通过这个完整的结构，固态核磁共振被证明是一种确定三维大分子结构的方法。
