Granwehr J, Urban J T, Trabesinger A H, Pines A
Materials Sciences Division, Lawrence Berkeley National Laboratory, Department of Chemistry, University of California, Berkeley, CA 94720, USA.
J Magn Reson. 2005 Oct;176(2):125-39. doi: 10.1016/j.jmr.2005.05.013.
Hyperpolarized (129)Xe can be used as a sensor to indirectly detect NMR spectra of heteronuclei that are neither covalently bound nor necessarily in direct contact with the Xe atoms, but coupled through long-range intermolecular dipole-dipole interactions. To reintroduce long-range dipolar couplings the sample symmetry has to be broken. This can be done either by using an asymmetric sample arrangement, or by breaking the symmetry of the spin magnetization with field gradient pulses. Experiments are performed where only a small fraction of the available (129)Xe magnetization is used for each point, so that a single batch of xenon suffices for the point-by-point acquisition of a heteronuclear NMR spectrum. Examples with (1)H as the analyte nucleus show that these methods have the potential to obtain spectra with a resolution that is high enough to determine homonuclear J couplings. The applicability of this technique with remote detection is discussed.
超极化（129）Xe可作为一种传感器，间接检测既非共价结合也不一定与Xe原子直接接触，但通过长程分子间偶极-偶极相互作用耦合的异核NMR谱。为了重新引入长程偶极耦合，必须打破样品对称性。这可以通过使用不对称样品排列，或通过场梯度脉冲打破自旋磁化的对称性来实现。所进行的实验中，每个点仅使用一小部分可用的（129）Xe磁化强度，因此一批氙就足以逐点采集异核NMR谱。以（1）H作为分析物核的例子表明，这些方法有潜力获得分辨率足够高以确定同核J耦合的谱。讨论了这种远程检测技术的适用性。
