Borcik Collin G, Price Lauren E, Heinrich John P, Stringer John A, Rienstra Chad M
Department of Biochemistry, University of Wisconsin-Madison, Madison, WI, United States of America; National Magnetic Resonance Facility at Madison (NMRFAM), University of Wisconsin-Madison, Madison, WI, United States of America.
PhoenixNMR, Loveland, CO, United States of America.
J Magn Reson. 2025 Sep;378:107919. doi: 10.1016/j.jmr.2025.107919. Epub 2025 Jun 9.
Proton (H) detection methodologies in solid-state NMR (SSNMR) have revolutionized the field allowing for probing of new frontiers in determining the structure and dynamics within biological systems and materials. While approaches that maximally leverage the high gyromagnetic ratio of H detection have enhanced sensitivity and resolution of SSNMR experiments, the radiofrequency (rf) circuit of magic-angle spinning (MAS) probes is not well optimized for H detection, limiting the overall signal-to-noise ratio (SNR). Rather, SSNMR probes have historically been optimized for lower gamma nuclei such as C and below. Here we present a design with an inner coil for proton (H) to maximize H sensitivity. Optimizing the H channel resulted in a 1.33-2-fold increase in SNR with H detection in a one-dimensional experiment. An outer coil is tuned to the C and N frequencies, with excellent B homogeneity on all three channels. Using this design, we find that the sensitivity scales better than the theoretical expectations from 600 MHz to 750 MHz, due to a combination of the improved rf efficiency and B homogeneity. We also demonstrate these improvements on a model protein system (GB1) with a 4D experiment collected in less than a day.
固态核磁共振（SSNMR）中的质子（H）检测方法彻底改变了该领域，使得在确定生物系统和材料内部的结构与动力学方面能够探索新的前沿。虽然最大限度利用H检测的高旋磁比的方法提高了SSNMR实验的灵敏度和分辨率，但魔角旋转（MAS）探头的射频（rf）电路针对H检测并未得到很好的优化，限制了整体信噪比（SNR）。相反，历史上SSNMR探头是针对诸如C及更低的低γ核进行优化的。在此，我们展示一种带有用于质子（H）的内线圈的设计，以最大化H灵敏度。在一维实验中对H通道进行优化后，H检测的SNR提高了1.33至2倍。一个外线圈调谐到C和N频率，在所有三个通道上具有出色的磁场均匀性。使用这种设计，我们发现由于rf效率的提高和磁场均匀性的综合作用，灵敏度从600 MHz到750 MHz的提升比理论预期更好。我们还在一个模型蛋白系统（GB1）上展示了这些改进，通过在不到一天的时间内采集的一个四维实验得以证明。
