Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful technique of providing information about the structure of the materials in the atomic scale as well as the dynamics within those materials, by which it is extensively used in material science and structural biology.

High magnetic field can promote NMR sensitivity and spectral resolution on one hand and on the other hand challenges the probe design, which is noticeably manifested by decreased B1 field homogeneity, limited B1 field strength, strong electric field “cooking” or damaging biologic samples. All the above eventually lead to the loss of sensitivity, which is intrinsically poor and needs to be continually improved by NMR community.

Recently, researchers from the High Magnetic Field Laboratory, Chinese Academy of Sciences (CHMFL) built a 600 MHz 1H/X double resonance static probe, which is able to produce very homogeneous and strong radio-frequency magnetic field (i.e. RF magnetic field or B1 field) while reduce the electric field to the utmost extent.

Through introduction and integration of techniques, such as cross-coil and balanced circuit, into the design, the probe achieves great improvement over conventional probes. Firstly, 1H channel B1 homogeneity measured by the ratio of signal intensities for an 810° pulse versus a 90° pulse (A810/A90) is around 96%. The maximum decoupling field is 132 kHz * 80 ms. RF power loss in 0~1000 mM NaCl solution is 0.02 mW·kHz-2·mM-1, which is only 10% of that in conventional probes that use a 6-turn solenoid, so significantly reduces the RF heating. Secondly, X channel is truly wideband and can cover frequency up to 31P. B1 homogeneity A810/A90 is around 83%. Finally, 13C sensitivity of Adamantane static CP spectrum recorded by this probe and a commercial 4 mm MAS probe are 88 and 46, respectively, showing a much increase in sensitivity of X channel detection.

This probe will open to users worldwide. For scientists who work on material science, aligned membrane proteins and low-γ NMR at high-field, our high sensitive static probe might help.

This work was partially supported by National Natural Science Foundation of China.

600 MHz 1H/X double resonance static probe (Image by LI Yunyan)