van Beek Jacco D, Dupree Ray, Levitt Malcolm H
School of Chemistry, Southampton University, Highfield, Southampton, SO17 1BJ, UK.
J Magn Reson. 2006 Mar;179(1):38-48. doi: 10.1016/j.jmr.2005.11.003. Epub 2005 Nov 23.
We have performed magic-angle-spinning solid-state NMR experiments in which protons are recoupled to oxygen-17 nuclei by applying a symmetry-based recoupling sequence at the proton Larmor frequency. Two-dimensional quadrupole-dipole correlation spectra are produced, in which the second-order quadrupolar shift of the oxygen-17 central transition is correlated with the recoupled heteronuclear dipole-dipole interaction. These spectra are sensitive to the relative orientation of the electric field gradient at the site of the oxygen-17 nucleus and the O-H internuclear vector. We also demonstrate experiments in which polarization is transferred from protons to oxygen-17, and show that oxygen-17 signals may be selected according to the protonation state of the oxygen site. We discuss the small observed value of the heteronuclear dipolar splitting in the central-transition oxygen-17 spectra.
我们进行了魔角旋转固态核磁共振实验，其中通过在质子拉莫尔频率下应用基于对称性的重新耦合序列，使质子与氧 - 17核重新耦合。生成了二维四极 - 偶极相关谱，其中氧 - 17中心跃迁的二阶四极位移与重新耦合的异核偶极 - 偶极相互作用相关。这些谱对氧 - 17核位置处的电场梯度与O - H核间矢量的相对取向敏感。我们还展示了极化从质子转移到氧 - 17的实验，并表明氧 - 17信号可根据氧位点的质子化状态进行选择。我们讨论了在中心跃迁氧 - 17谱中观察到的异核偶极分裂的小值。
