Opella S J, Nevzorov A, Mesleh M F, Marassi F M
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093-0307, USA.
Biochem Cell Biol. 2002;80(5):597-604. doi: 10.1139/o02-154.
Current strategies for determining the structures of membrane proteins in lipid environments by NMR spectroscopy rely on the anisotropy of nuclear spin interactions, which are experimentally accessible through experiments performed on weakly and completely aligned samples. Importantly, the anisotropy of nuclear spin interactions results in a mapping of structure to the resonance frequencies and splittings observed in NMR spectra. Distinctive wheel-like patterns are observed in two-dimensional 1H-15N heteronuclear dipolar/15N chemical shift PISEMA (polarization inversion spin-exchange at the magic angle) spectra of helical membrane proteins in highly aligned lipid bilayer samples. One-dimensional dipolar waves are an extension of two-dimensional PISA (polarity index slant angle) wheels that map protein structures in NMR spectra of both weakly and completely aligned samples. Dipolar waves describe the periodic wave-like variations of the magnitudes of the heteronuclear dipolar couplings as a function of residue number in the absence of chemical shift effects. Since weakly aligned samples of proteins display these same effects, primarily as residual dipolar couplings, in solution NMR spectra, this represents a convergence of solid-state and solution NMR approaches to structure determination.
目前通过核磁共振光谱法在脂质环境中测定膜蛋白结构的策略依赖于核自旋相互作用的各向异性，这种各向异性可通过对弱排列和完全排列样品进行的实验在实验上获得。重要的是，核自旋相互作用的各向异性导致结构与核磁共振谱中观察到的共振频率和分裂之间的映射关系。在高度排列的脂质双层样品中，螺旋膜蛋白的二维1H-15N异核偶极/15N化学位移PISEMA（魔角极化反转自旋交换）谱中观察到独特的轮状图案。一维偶极波是二维PISA（极性指数倾斜角）轮的扩展，可在弱排列和完全排列样品的核磁共振谱中绘制蛋白质结构。偶极波描述了在不存在化学位移效应时，异核偶极耦合大小随残基编号的周期性波状变化。由于蛋白质的弱排列样品在溶液核磁共振谱中也表现出这些相同的效应，主要表现为残余偶极耦合，这代表了固态核磁共振和溶液核磁共振结构测定方法的融合。
