Hong M, Gross J D, Hu W, Griffin R G
Francis Bitter Magnet Laboratory and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
J Magn Reson. 1998 Nov;135(1):169-77. doi: 10.1006/jmre.1998.1573.
We demonstrate a dipolar-chemical shift correlation technique for sign-sensitive determination of the torsion angle phi in solid peptides and proteins under magic-angle spinning. The indirect dimension of the experiment is obtained by separate but synchronous evolution of the magnetization under the 15N chemical shift and the C-H dipolar coupling. The resulting sum and difference spectrum of the two frequencies, with more than ten independent sidebands, depends strongly on the relative orientation of the 15N chemical shift tensor and the Calpha-Halpha bond. This relative orientation reflects the C(O)i-1-N-Calpha-C(O)i torsion angle. The technique can distinguish phi angles over the full range of 360 degrees when the amide 15N chemical shift tensor does not possess reflection symmetry with respect to the peptide plane. Thus it complements our previous HNCH experiment, in which two mirror-symmetric conformers of the HN-N bond relative to the Calpha-Halpha bond around the N-Calpha axis cannot be distinguished.
我们展示了一种用于在魔角旋转下对固体肽和蛋白质中的扭转角φ进行符号敏感测定的偶极 - 化学位移相关技术。该实验的间接维度是通过在¹⁵N化学位移和C - H偶极耦合下对磁化强度进行单独但同步的演化来获得的。两个频率的所得和差谱，具有十多个独立边带，强烈依赖于¹⁵N化学位移张量与Cα - Hα键的相对取向。这种相对取向反映了C(O)i - 1 - N - Cα - C(O)i扭转角。当酰胺¹⁵N化学位移张量相对于肽平面不具有反射对称性时，该技术可以区分360度全范围内的φ角。因此，它补充了我们之前的HNCH实验，在该实验中，围绕N - Cα轴的HN - N键相对于Cα - Hα键的两个镜像对称构象无法区分。
