Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Gustav Wieds Vej 14, DK-8000 Aarhus C, Denmark.
Nanonord A/S, Skjernvej 4A, DK-9220 Aalborg Ø, Denmark.
J Magn Reson. 2014 Jan;238:20-5. doi: 10.1016/j.jmr.2013.10.015. Epub 2013 Nov 1.
Mobile and cost-effective NMR spectroscopy exploiting low-field permanent magnets is a field of tremendous development with obvious applications for arrayed large scale analysis, field work, and industrial screening. So far such demonstrations have concentrated on relaxation measurements and lately high-resolution liquid-state NMR applications. With high-resolution solid-state NMR spectroscopy being increasingly important in a broad variety of applications, we here introduce low-field magic-angle spinning (MAS) solid-state multinuclear NMR based on a commercial ACT 0.45 T 62 mm bore Halbach magnet along with a homebuilt FPGA digital NMR console, amplifiers, and a modified standard 45 mm wide MAS probe for 7 mm rotors. To illustrate the performance of the instrument and address cases where the low magnetic field may offer complementarity to high-field NMR experiments, we demonstrate applications for (23)Na MAS NMR with enhanced second-order quadrupolar coupling effects and (31)P MAS NMR where reduced influence from chemical shift anisotropy at low field may facilitate determination of heteronuclear dipole-dipole couplings.
利用低场永磁体实现移动且经济高效的 NMR 光谱学是一个发展迅速的领域，在阵列式大规模分析、现场工作和工业筛选方面具有明显的应用。到目前为止，此类演示集中在弛豫测量和最近的高分辨率液相 NMR 应用上。随着高分辨率固态 NMR 光谱学在广泛的应用中变得越来越重要，我们在这里介绍了基于商用 ACT 0.45 T 62 毫米孔径 Halbach 磁铁的低场魔角旋转（MAS）固态多核 NMR，以及自制的 FPGA 数字 NMR 控制台、放大器和改装的标准 45 毫米宽 MAS 探头，用于 7 毫米转子。为了说明仪器的性能，并解决低磁场可能对高场 NMR 实验具有互补性的情况，我们展示了（23）Na MAS NMR 的应用，其中增强的二阶四极偶合效应和（31）P MAS NMR 中低磁场下化学位移各向异性的影响降低，有助于确定异核偶极-偶极耦合。
